BILD 2

What is a neuron’s basic structure and function?

Dendrite: receive signal from other neurons

Soma: Cell body

Axon Hillock: signal generates/action potential starts

Axon: signal travels across

Myelin Sheath: Insulates axon, sends signal faster, oligodendrocytes (CNS) or Schwann cells

Node of ranvier: gaps between the myelin sheath, where the action potential will jump to
axon terminal: the signal exits, neurotransmitter are

What are other types of cells in the nervous system besides the neuron?

• Glial cells: support neurons, induce formation of blood brain barrier, repair brain injuires, can specialize into oligodendrocytes

• Ganglia: simple cluster of neurons wehre information integration takes place in the PNS

Where are differences btwn the CNS and PNS

CNS

• brain and spinal cord

• oligodendrocytes

• integration of information

PNS

• Everything else, sensory nerves

• carries information to and from CNS (Afferent Division and Efferent Division)

What is the basic pathway of neurons processing information

Input —> Integration → output

Internal and external stimuli —> sensory receptors —> afferent division —> CNS —> Efferent Division —> Autonomic Nervous system or Motor system—> output

How is information transmitted/process?

through electrical signals

neurons get excited —> alter membrane permeability through channels —> change in membrane potential —> signal

What is membrane potential

• voltage difference btwn the inside and outside of the cell

• the separation of opp charges across the plasma membrane

• measured in mV

• uses leak channels and voltated gated

What is resting membrane potential

• voltage diff when the cell is at rest

• influenced by a permability of Na+ and K+

• More K+ channels than Na+

• Na+ is outside the cell naturally

• K+ is inside the cell naturally

• regulated by the sodium potassium ATPase pump

• uses leak ion channels and ion pumps

What are the two types of membrane potential changes

Graded potential

• short distance signals

• depolarization and hyperpolarization

• decays with distance from source

• magnitude depends on strength of stimulus

• no refactory period

• a stimulus acts on a neuron, causing graded potential where ligand gated channels open and ions enter, this ion movement (if strong enought) reaches a threshold and action potential starts

• ligand gated

Action Potential

• long distance

• all or nothing; constant magnitude w/o losing strength

• does not decay

• absolute refactory and relative refactory period

• voltage gated

What is depolarization, repolarization, and hyperpolarization

Depolarization: membrane potential becomes less negative (more +)

Repolarization: returns to resting potential

Hyperpolarization: membrane potential becomes more negative

What is the basic outline of an action potential

Resting potential —> stimulus —> threshold potential —> Na+ voltage ion gates open, Na+ gets into the cell —> K+ voltage gates open —> Na+ gates inactive —> hyperpolarization —> resting potential, K+ closes

How does a voltage gated Na+ and K+ channels open/move during action potential

• change in membrane potential/voltage opens these gates

• Na+ comes into the cell

• K+ leaves the cell

how is an action potential conducted along the axon?

Sodium channels depolarize neighboring regions by bringing these regions to threshold potential

inactive sodium channels during relative refactory period behind the zone prevent action potential from moving back

What is salatory conduction?

action potential jumps from node of ranvier. note: action potential is a domino effect where one action potential will start another action potential at another node

What is an absolute and relative refactory period?

absolute: cannot restimulate/start a second action potential bc Na+ channels are inactive (remember this is what starts the action potential)

relative: can be restimulated for a second one but needs a stronger stimulus. its bc Na+ channels are at rest and closed and can be reopened

What happens after action potential? How does it get back to resting potential?

Sodium potassium pump to balance ions and charges

3 Na+ moves out of the cell

2 K+ moves inside the cell

req ATP

Synaptic communication, what happens at the axon terminal

• action potential reaches axon terminal

• Ca2+ channels open and get inside the cell

• causes it to release neurotransmitters in vesicles

• goes to synapse then receptors’

• recycled or broken down

What are post synaptic potentials? What are the most effective ones

• changes in the membrane potential of post synaptic neuron. graded potentials! influxation of ions creates these post-synpatic potentials, these converge at the hillock and neuron summates signals

• Excitatory postsynaptic potential (EPSPs): depolarization that brings membrane potential towards threshold

• Inhibitory postsynaptic potentials (IPSPs): hyperpolarization that brings potential away from threshold

• Temporal Summation: two rapid ESP in succession

• Spatial Summation: two diff ESP produced simultaneously

What does the brain do? what parts are in the forebrain, midbrain, and hindbrain

regulate homestasis, awareness, movement, cog, emotions

forebrain: cerebrum (cerebral cortext. white and grey matter)

midbrain: connects fore and hind

hindbrain: pons, cerebellum, medulla oblongata

What does the cerebrum do? what is cerebral cortext, grey and white matter

language, cog, memory, conciousness

cerebral cortext: receives input from sensory organs and somatosensory organs

grey matter: neuron cell bodies, process data, memory thoughts

white: axon, commuication network ofrom grey and rest of body

what is lateralization

left side dominant for lang, math, logical

right dominat for pattern, recognition

exchange info thorugh corpus callosum

What are the four lobes

• Occipital lobe: visual

• temporal lobe: auditory

• parietal: reception and perception of somatosensory

• frontal: volunatry movemnt, thinking

What does the thalamus, hypothalamus, brain stem, and cerebellum do?

thalamus: senses stimuli, synpatic integration center

hypothalamus: homeostatsis, internal environment

brain stem: cardiovasular, digestive, and respiratory

cerebellum: balance and coordination

What is the biological clock regulation?

circadian rhythm is regulated in hypothalamus by suprachiasmatic nucleus

What is arousal and sleep and memory/emotions regualted

arousal and sleep: controlled by midbrain and pons

memory and emotion: amygdala, hippocammpus, thalamus

What does the spinal cord do?

link between CNS and PNS, integrating center for spinal reflexes (withdrawl reflex)

What protects the CNS

• mengines: three layers

• Cerebrospinal fluid: cushioning fluid

• blood-brain barrier: limits access of blood-borne material into brain tissue

What is neural plasticity

nervous system can be modified after birth

changes happen at synapses and can strenghten or weaken signaling

What are the different neurotransmitter pathways in the brain

Norepinephrine: sleep, learning, memory

Serotonin: emotion

Dopamine: reward center

What is the brains reward center and drugs

collection of structures and pathways that are responsible for desire, motivation, etc

cocaine/amphatamine: block dopamine from removal in clef

Opium/heronin: stops inhibitor

Nicotine: stimualte dopamine

Define the somatic and visceral components of the PNS

Somatic: brings sensory info from skeletal muscle, joints, and skin

Visceral: monitors other internal tissues like smooth muscles, cardiac muscle, glands

What is the first step in the sensory pathway?

Sensory reception: detects stimuli

What is the second step in the sensory pathway?

Sensory transduction

• Receptor potential: stimulus causes a change in membrane potential

• Graded potential!

• Neuronal Receptor: sends signal directly to the CNS, larger change in receptor potential = more frequent

• Non-neuronal Potential: uses neurotransmitters, larger change in receptor potential = more neurotransmitters released

What is the third step in the sensory pathway?

Perception

• the brains construction of stimuli

• the path of the action potential is how the brain distinguishes stimulli

• cerebral cortex receives input from sensory organs

What is the fourth step in the sensory pathway?

Modification

• Amplification: strengthening of stimulus energy by cells in sensory pathways

• Adaptation: decrease in responsiveness to continued stimulation

What are the 6 types of sensory receptors

• Mechanoreceptors: non-neuronal, sound, touch, pressure, motion

• Electromagnetic receptors/ photo receptors: light, electricity, magnetism

• Thermoreceptors: heat and cold; skin receptors and ant. hypothalamus sends info to post hypothalamus

• Pain receptors (Nociceptors): trigger defense mechanisms; neuronal

• Osmoreceptors: changes in solute conc; hypothalamus

• Chemoreceptors

  • Smell (Olfaction): detection of order in the air; neuronal

  • Taste (Gustation): dectant of tastants in solution; non-neuronal

How is hearing detected by mechanoreceptors

1. Sound (moving particles in air) enters the outer ear into the canal

2. Vibrates the tympanic membrane

3. transmits vibration to the middle ear: Malleus, Incus, Stapes

4. transmits vibration to the oval window of the cochlea

5. pressure waves move through cochlea fluid

6. fluid movement bends the hair cells in the organ of Corti

7. Depending on the direction of the hair, the bending causes ion channels to open and close and release or release less of neurotransmitters

8. generates an action potential to the auditory nerve to the CNS

9. goes through thalamus

10. goes to auditory cortex in temporal lobe

How is body equilibrium maintained? (mechanoreceptors)

• three semicircular canals on cochela detect angular movements in any direction

• Utricle and saccule detect linear motion and position relative to gravity

1. fluid movement in vesibular sense organs

2. hair cells bend and produces an action potential

3. signals carries to vestibulocochelar nerve to brainstem and cerebral regions

What are the parts of the eye

Pupil: light enters

Iris: controls how much light enters the pupil by constricting or dilating the pupil

Scalera: protection of the eye

Lens: focuses the light to send to the retina

Ciliary body: can contract and alter the shape of the lens to focus light on near or far objects

How is light travel in the eye

Light enters pupil

focuses through the lens

sent to the retina

What are the three components of the retina

Rods and cones

Bipolar cells: has synpases between the two

ganglion cells: bundles of axon form optic nerve

What is the structure of rods and what do they do?

Rods is where the light enters bc it has photoreceptors

• outer structure: detects light stimulus, has photopigment molecules, faltten membranous disc, contains rhodopsin (opsin and retinal)

• Inner structure: metabolic structure

• Synaptic terminal: releases neurotransmitters to bipolar cells; depends if it is light or dark

What do cones do?

Three types of cones have three diff visual pigments: red, green, blue

Red and green color blindness is sex linked on X chromosomes

What happens in the eye when it is dark?

• Photoreceptor ion channels are opened

• dark photoreceptors are depolarized and releases inhibitory neurotransmitters onto the bipolar cells

• bipolar cells cannot fire anymore

• brain detects this as dark

• cis retinal structure

What happens in the eye when it is light?

Recall: Rods have photoreceptor pigments

• light travels to retina

• activates photopigments (rhodopsin changes to a trans position)

• photoreceptors hyperpolarized

• does not send the inhibitory neurotransmitter

• bipolar cell can activate and release neurotransmitters

• signal sent to ganglion cells and into the optic nerve

What is the efferent division of the PNS and two parts?

Carries motor commands from the CNS to target muscles and glands

Autonomic Nervous System and Somatic Nervous System (motor)

What is the autonomic nervous system?

• controls smooth and cardiac muscles, glands

• involuntary movement

• sympathetic and parasympathetic nervous system; dual innervation, antagonistic control

• works with endocrine and behavioral state systems to maintain homeostasis

What is the autonomic nervous system pathway? What neurons?

Two neuron chain: preganglionic axon and postganglionic axon

• Preganglionic axon extends from CNS

• Postgangolionic axon extends to target tissue

• SNS: short preganglionic axons w/ long ganglionic axons, preganglionic axon physically extends from CNS and leaves through spinal nerves (T1-L2), ganglia are usually near spinal cords

• PNS: long preganglionic axons w/ short ganglionic axons, pre axons have their cell bodies in brain stem and physically extends from CNS and leaves through crainal nervers and sacral spinal cord, ganglia are near or within target

what is the SNS and PNS

SNS
- flight or flight

• inc heartrate, inc breathing, decreases motility of digestion

PNS

• rest and digest

• dec heartrate, bdecbreathing, inc motility of digestion

What is the difference btwn the Sympathetic and Parasympathetic neurotransmitters?

Both use acetylcholine for their preganglionic axons to ganglionic axon with nicotinic cholinergic receptor

SNS: uses norepinephrine for their postganglionic axon to target tissue with an adrenergic receptors

PNS: uses Ach for their postganglionic axon to target tissue with a muscarinic receptor

What is the basic anatomy of a skeletal muscle?

• Thick filaments (myosin) and thin filaments (actin) make up the unit of a sacromere

• Sacromere makes up a myofibril

• Bunch of myofibril make up muscle fiber

• bundle of muscle fiber makes up muscle

What is the pathway to a target muscle?

CNS axon extends to the target muscle and relases Ach to nicotinic receptors

What does the neuromuscular junction consist of

axon terminal (somatic neuron branches), motor end plate (receptors), schwann cells

What is the muscle contraction process?

1. Action potential arrives at the end of the neuron

2. Releases Ach (from Ca2+ channels) into the synpase

3. Ach binds to the ligated nicotinic channels

4. causes sodium voltage gated channels to open and starts action potential

5. action potential travels down T-tubules which signals the sacroplasmic reticulum to relase Ca2+ into the cytosol

6. Ca2+ binds with troponin and allows myosin to bind with actin

7. filaments pull close together, causing a contraction

8. ATP binds with myosin head to stop and lower its position

What is excitation-contraction coupling

events that link muscle excitation and contraction, Ca2+ is the link

What are chemical agents and diseases that affect neuromusclar junctions?

Botulinum toxin blocks release of Ach

Curae blcoks Ach receptor

Myasthenia gravis, autoimmune disease that destorys Ach receptors

black window venom causes excess release

organophosphate inhibits AchE

How does skelton support muscles

muscles attach to skeleton

provide support, movement

antagonistc pairs

What is a behavior

an action carried out by muscles under the control of the CNS

behavior can affect survivial and reproduction, thus under natural selection

What is the endocrine system composed of?

• Ductless endocrine glans

• Central Endocrine glands: pineal, hypothalamus, pituitary

• Peripheral Nervous glands

• Pituitary, thyroid, and adrenal glands are solely endocrine functions

What are the endocrine system’s functions?

• mediated by hormones

• Control and integrate both the digestion and absorption of food and circulation

• regulates metabolism (insulin and glucagon)

• regulates red blood cell production

• promotes sequential growth and development

• controls reproduction

• regulates H2O and electrolyte balance

• Help body cope with stressful situations

What are hormones? Why do the same hormones have diff responses? Give an example using epinephrine

• Chemical messengers secreted by endocrine glands into the blood stream to transport signals to distant target cells

• Cells with certain receptors can respond to certain hormones

• Same hormone can have different responses due to different receptors types or in the molecules that produce the response in target cells

Epinephrine on Adenergic Beta receptor on liver cell

• Causes glycogen to break down glucose and release it

Epinephrine on Adnergic Beta receptor on skeletal muscle blood vessel

• vessel dilates

Epinephrine on alpha receptor on intestinal blood vessel

• constricts vessel

What are the different types of hormones?

Hydrophilic hormones

• binds to membrane proteins and uses receptors, can manipulate protein expression. Ex: peptides (Insulin), catecholamines (norepinephrine)

Lipophilic

• can penetrate through plasma membrane and travel directly to nucleus by a receptor complex moving inside the nucleus, alter gene expression. Ex: steroid hormones (sex hormones like testerone), thyroid hormones

Tropic hormones: a hormone can regulate secretion of another hormone from another endocrine gland

What is a simple endocrine pathway using pH control and digestive enzyme secretion in duodenum? Where is the exocrine portion of the pancreas and where is the endocrine?

Local stimulus → endocrine cell —> release hormone —> blood vessel —> targeting cell —> response

pH control

1. Stimulus: low pH (acidic) —> In the duodenum mucosa, S cells secrete secretin —> travel on blood vessel —> pancreatic duct cells (target cell) —> releases bicarbonate in duodenum to neutralize acid

Digestive Enzymes

2. Stimulus: proteins and fats in duodenum —> In the duodenum mucosa, I cells secrete CCK —> travel on blood vessel —> Pancreatic acinar cells (target cell) —> release enzyme

Exocrine = ducts — duct and acinar cells

Endocrine = blood — secrete insullin and glucagon

What is a simple endocrine pathway using blood glucose and energy metabolism regulation

Local stimulus → endocrine cell —> release hormone —> blood vessel —> targeting cell —> response

Insulin

1. Stimulus: Inc blood glucose —> Pancreatic Beta cells located in the Islets of Langerhans release Insulin —> travel through blood stream —> act on target cell/tissues —> dec blood glucose levels

Glucagon

1. Stimulus: Low blood glucose —> Pancreatic Alpha cells in the Islets of Langerhans release glucagon —> travel through blood stream —> act on target cell/tissues —> inc blood glucose lvls

What is a neuroendocrine pathway? Use thyroid hormones and infant suckling as examples

• responds to stimuli from the external/internal environment and relay on a sensory in the nervous system

• Neurosecretory cells: receive neuron impulses but releases hormones into the blood stream (hypothalamus)

Regulation of thyroid hormones

1. Stimulus: low thyroid levels, cold, etc —> sensory neuron detects —> information sent to hypothalamus —> action potential from this causes hypothalamus to release hormones: Thyrotropin-releasing hormone (TRH) —> sent to portal system (blood stream) —> Anterior pituitary —> causes the Ant. pituitary to release Thyroid-stimulating hormone —> acts on thyroid gland —> thyroid gland releases thyroid hormone (T3, T4) —> target body cells inc metabolism and heat production

*Negative feedback

Infant Suckling

1. Stimulus: infant sucking —> sensory nerves in nipples detect —> hypothalamus and their axons extend all the way down to the post. pituitary gland —> release oxytocin technically from the post. pituitary gland —>travel in blood stream —> acts on smooth muscle in mammary gland —> milk release

*Positive feedback

*Prolactin makes milk, oxytocin secretes it

How does the hypothalamus and pituitary glands work together?

• Hypothalamus integrates both the nervous system and endocrine system

• Signals from the hypothalamus travel to the pituitary gland located at its base

• hypo controls the release of hormones of the ant. and post. pituitary glans

• Hypo secretes hypophysiotrophic hormones (releasing or inhibitory hormones) into portal systems (a specialized network of blood vessels that directly connects the hypothalamus to the anterior pituitary gland)

What does the anterior pituitary gland produce and secrete?

• The hypothalamus hormones target the ant. pituitary gland to release their hormones

• Thyroid-stimulating hormone (TSH): tropic hormone, tells thyroid gland to release thyroid hormone, T3, T4

• Adrenocorticotropic Hormone (ACTH): tropic hormone, tells adrenal gland to release cortisol

• Follicle-stimulating hormone (FSH) and Luteinzing Hormone (LH): tropic hormone, tells gonads (ovaries or testes) to secrete sex hormones (estrogen and progesterone or testosterone, and also ova or sperm)

• Growth Hormone (GH): tropic hormone, tells liver to release IGF1, which affects bone and soft tissue and causes growth

• Prolactin (PRL): non tropic, tells mammary gland to produce milk

What does the posterior pituitary gland do?

• Stores two small peptide hormones (Vasopressin and Oxytocin) which are made in the Hypothalamus

• The Hypothalamus axons extend to the neuronal terminals in post pituitary — release Vasopressin and Oxytocin

• Vasopressin: act on nephrons in kidney and increase permeability of distal and collecting tubules to H2O (conserve water during urine), or acts on arterioles and causes vasoconstriction (narrowing)

• Oxytocin: acts on uterus to stimulate uterine contractions during childbirth or mammary glands for ejecting milk

What do the thyroid gland and hormones do?

Thyroid gland contains two types of endocrine secretory cells

• Follicular cells produce thyroid hormones T3 and T4

• C cells produce calcitonin which secretes in response to an increase plasma Ca2+, and lwrs it by inhibiting the activity of bone osteoclats

Thyroid hormones

• main determinant of basal metabolic rate

• plays crucial role in normal development of nervous system

• essential for normal growth

• These hormones tell nearly every cell in your body how fast to turn food and oxygen into usable energy, dictating how many calories you burn at rest, how energetic you feel, and how your body stores or uses weigh

What does the adrenal gland do and secrete?

• It is involved in nutrient metabolism and stress adaptation

• Adrenal Cortex: secretes steroid hormones (lipohilic)

• Adrenal Medulla: secretes catecholamines (hydophilic), Epinephrine 80%, Norepinephrine 20%

• Steroid hormones

  • Aldosterone: helps maintain salt balance and blood pressure

  • Cortisol: involved in stress resistance and anti-inflammatory effects

  • Sex hormones: regulate sex drive

• Catecholamine (Epinephrine)

  • reinforces sympathetic effects

  • maintain arterial blood pressure

  • inc blood glucose and fatty acids

What is the neuroendocrine reflex? Use stress response as an example (short vs long)

A bodily response that links the nervous system and the hormone system

EX: Stress response: A generalized nonspecific response of the body to any factory that overwhelms or threatens to overwhelm the body’s ability to maintain homeostasis

• Short term stress: sends nerves impulse down spinal cord through preganglionic fibers—> adrenal medulla —> secrete catecholamines (epinephrine and norepinephrine)

• Long term stress: sends signal to hypothalamus —> releases Corticotropin hormone (CRH) onto ant pituitary —> releases ACTH onto adrenal cortex —> secretes steroid hormones (cortisol)

• * Note Vasopressin can also work with CRH to ramp up production of ACTH

What regulates hormone secreation?

Hierarchic chain of command: chain of hormonal communcation

Feedback control

• negative: targets gland hormones and inhibits hypothalamic and ant. pituitary secretion, in simple pathway it stops the stimulus

• positive: enhances response

Circadian rhythm: regulated by suprachiasmatic nucleus, reguaates concentration during light and dark

What are some examples of endocrine dysfunction?

Hypothyroidism

• Causes: failure of thyroid gland, secondary cause due to deficient TRH and TSH, inadequate supply of Iodine (produces T3 and T4)

• Energy and Weight: Constant fatigue, sluggishness, and unexpected weight gain.

• Treatment: replacement thyroid hormone, dietary Iodine

Hyperthyroidism

• Causes: Grave’s Disease (body produces thyroid stimulating immunoglobins which bind and continue secretion), secondary cause is excess TRH and TSH

• Weight changes: Losing weight fast even with a big appetite. — break down storage

• Digestion: More frequent bowel movements or loose stools. — contract faster

• Treatment: removal of over-secreting thyroid lobe, radioactive iodine/anti-thyroid drugs

What is the evolution of the hormone function?

• Thyroid hormone in frogs stimulate the reabsorption of tadpole tails during metamorphosis

• Prolactin in birds regulate fat and metabolism, freshwater fish regulate salt and water balance

What are the functions of the digestive system? Which parts are regulated and why

• Transfer nutrients, water, and electrolytes from ingested food into the bodys internal enviroment

• Digestion: Biochemical (enzygmatic) breakdown of complex foodstuffs into absorbable units

• Absorption: The end-products of digestion that is transferred from the digestive tract lumen into blood stream to specific regions

  • Secretion: the release of water, electrolytes, and specific organic constituents (enzyme) by cells and organs, released onto digestive tract through neuronal or hormonal stimulation, reabsorbed back into blood after digestion complete

  • Motility: muscular contraction that mix and move food forward

    • propulsion: pushing content forward

    • mixing: mixing food with digestive fluid

    • mass movement: happens in large intestine, intense and prolonged contractions, clear the large intestine

Secretion and motility regulated bc nothing stops digestion and absorption (passive) also bc of acidic enzymes

What are the digestive compartments?

• Specialized compartments where food breaksdown

• Intracellular digestion: Lysosomes breaking down food, waste, pathogens in cell

• Extracellular digestion: breakdown of food outside of cells in cavity or tube

  • Gastrovascular cavity: not in humans, same hole for digesting and excretion, ex: flatworm

  • Digestive tract: food travels from mouth to anus

  • Accessory organs: help with digestion but food does not travel here, Ex: pancreas, gall-bladder, salivary glands, liver

  • Oral cavity with salivary glands (amylase)

  • Esophagus

  • Stomach

  • Small intestine

  • Large intestine

What is the anatomy of the digestive tract

• Lumen: hallow space in digestive tract

• Serosa: Outer connective tissue, secretes serosa fluid that lubricates prevents friction, continous w/ mesentary

• Muscularis externa: major smooth muscle in the wall

  • Outer longitudinal muscle: can shorten the length of the GI Tube through contraction

  • Inner circular muscle: can shorten/dec diameter of the lumen through contraction

• Myenteric plexus: network of nerves in between these two layers

• Submucosa: thick connective tissue, provides distensibililty (stretch), and elasticity, has large blood and lymph vessels

• Submucosal plexus: nerve network

• Mucosa: lines luminal surface of digestive tract

  • Muscularis mucosa: outer, smooth muscle

  • Lamina propria: thin middle layer connective tissue

  • Mucous membrane: inner endothelial layer

How is digestion regulated? talk abt the two systems and hormones

• neural and hormonal inputs

• Enteric Nervous System

  • Nerve network in GI tract — submucosal plexus and myenteric plexus

  • autonomous from CNS, regulates content, movement of smooth muscle,

  • controls muscle and secretion of glands

  • does communicate with CNS

• CNS influences digestive tract motility and secretion, can alter the lvl of hormone

• ENS and CNS communicate through nerve fibers of the ANS (sympathetic and parasympathetic branches)

• GI hormones: produced by specialized endocrine cells within mucosa

  • Ex: Peptides and amino acids causes the Stomach to release Gastrin from G Cells —> acts on ECL Cells and and parietal cells —> secretes gastric acid

  • Ex: Small Intestine releasing secretin and CCK (duodenum)

  • Ex: Intestine can release motilin which stimulates fasting —> acts on gastric and intestinal smooth muscle —> causes migrating motor complex to be stimulated (facilitates transportation of indigestible substances to large intestine)

What is the first step of the digestive pathway? What are special enzymes

Mouth: mechanically chewing and breaking down food, amylase (carbohydrate enzyme)

What is the second step of the digestive pathway?

Mouth —> Food travels to esophagus

What is the third step of the digestive pathway? Describe the three specific cells, gastric juices, and feedback

Stomach: store food, mixes food mechanically, secrete gastric juices which help break down food into chyme (soft food mix with digestive juices)

• has gastric gland which makes gastric jucies

  • Parietal Cells (bottom): secrete CI, cleaves (breakdown) pepsinogen from chief cells into active pepsin

  • Chief cells (middle): make and secrete pepsinogen (inactive form to stop body from digesting its own body protein)

  • Mucus cell (top): make and secrete mucus as a physical barrier from acidic gastric juices

• Gastric juices

  • HCI — low pH 2, denatures proteins

  • Pepsin — formed from HCI and pepsinogen mixing, breaks down the denatured protein into smaller pieces

  • Secretion of HCI from the parietal cells is controlled by Gastrin and can also be stimulated by acetycholine

Pathway

• Stimulus: proteins/food enter stomach —> G cells secrete Gastrin —> travels through blood stream —> act on ECL cell —> releases histamine —→ travel through blood stream —> act on parietal cell —> release HCI *enteric neurons can release acetylcholine on parietal cell —> Chief cells release pepsinogen —> HCI and pepsinogen mix —> active pepsin —> HCI and pepsin break down food —> chyme

Feedback loop

• Somatostatin-releasing cell can inhibit production of HCI

• Releases somatostatin which works to inhibit G cell, ECL Cell, and parietal cell

What is the fourth step of the digestive pathway? describe the pH and digestive enzyme control. talk about transport and villi

• Chyme enters Small intestine (major organ of digestion and absorption)

  • most digestion occurs at duodenum (first portion of small intestine)

  • Main absorption of nutrients and water happens in jujunum (middle) and ileum (terminal)

• pH control in duodenum — hormonal control

  • chyme is acidic and we need to neutralize it

  • Stimulus (low pH) —> S cells release secretin —> travels on bloodstream → pancreatic duct cell —> release bicarbonate —> neutralize chyme

• Digestive enzyme control in duodenum — hormal control

  • Stimulus (proteins and fats) —> I cells release CCK —> travel to bloodstream —> Pancreatic acinar cells —> release digestive enzyme —> food breakdown

• Chyme (after neutralization) will mix with other digestive fluids in pancreas, liver, gallbladder and intestinal wall

  • Pancreas: trypsin and chymotrypsin (break down proteins), amylase, lipase

  • Liver: makes bile (stored in gallbladder)

  • Intestinal wall: digestive enzymes that complete the digestion of carbs, fats, proteins

• Villi and microvilli in the intestinal lumen that create a brush border and inc the rate of nutrient absorption

• Small particles that are broken down enough will leave to the blood stream and to other regions using transport in jejunum and ileum (absorption)

  • Passive transport: simple and facilitated diffusion (req a facilitator or protein)

  • Active transport: primary and secondary (relay on atpase gradient, does not directly use ATP)

    • Ex: Glucose transport

      • ATPase pump, pumps out 3 Na+ and pumps in 2K+

      • Na+ wants to go back in the cell naturally and glucose also wants to enter

      • uses Sodium glucose cotransporter which brings them both in the cell

      • Glucose travels through the cell and moves out of the cell through facilitated diffusion of GLUT-2

      • *Fructose uses GLUT-5

    
    

• Pathway'

  • Chyme enters small intestine (duodenum) —> S cells release secretin —> travels on bloodstream → pancreatic duct cell —> release bicarbonate —> neutralize chyme —> Duodenum breaks down proteins—> I cells release CCK —> travel to bloodstream —> Pancreatic acinar cells —> release digestive enzyme —> food breakdown —> Chyme mixes with digestive fluids —>absorption in jejunum and ileum —> transporters take small particles into blood capillaries —> rest is sent to large intestine

What is the fifth step of the digestive pathway

Large intestine: four structural parts but we will focus on colon — recover water, vitamin K, salt that has entered the digestive tract, will turn into solid stool

• no secretion of digestive enzymes, no absorption of nutrients

• food enters through ileocecal valve

Motility

• Mass movements move the food forward and trigger the defacation reflex (stool moves into rectum

What is the sixth and seventh step of the digestive pathway

Rectum (stores pee and poop) —> anus

What are some disorders of the digestive system?

• Gastroparesis: delayed gastric emptying (food stays in stomach for too long), can be caused by glyconic control, or extrinisic or intrinisic neuropathy

• Constipation: infrequent bowel movement or difficult passage of stool, can be caused by inadequate fiber diets, depression, diabetes, meds,etc

• Diarrhea: loose, watery bowel movement, caused by viral parasitic infections, meds

• Gluten-senstive enteropathy (Celiac disease): autoimmune inflammatory disease that causes destruction enterocytes (epithelial cells of intestines), resulting in shortening of villi, gluten destroys lining

• Inflammatory bowel disease (Crohns, Ulcerative colitis): chronic inflammatory intestinal condition

Define nutrients

Chemical substances ini food that provide the energy for various body processes

• chemical energy is converted into ATP

• organic building blocks such as organic carbon and organic nitrogen synthesizes a variety of complex organic molecules in the body

Essential nutrients: must be obtained from dietary sources, cant be synthesized in the body

• essential amino acids: meat, egg, cheese,

• essential fatty acids: lionelic acid (Omega-6 found in vegetable oils) and alpha-lionelic acid (Omega-3 found in plant seeds and nuts)

6 Classifications: carbs, fats, proteins, minerals, vitamin, water

What is malnutrition and undernutrition

Malnutrition: long term absence of one or more essential nutrients from diet

Undernutrition: results when diet does not provide enough chemical energy

• used by stored fat and carbs

• breaks down its own protein, loss of muscle mass

• suffer protein deficiency of brain

• die or suffer irreversible damage

What hormones regulate appetite and consumption

• Ghrelin secreted by the stomach wall increase appetite

• Leptin produced by adipose tissue suppresses appetite

• GLP-1 produced by intestines promotes satiety/suppresses appetite

What is metabolism? what is catabolic and anabolic pathways

Sum of chemical reactions in the body

• extract energy from nutrients

• uses energy for work

• store excess energy

Catabolic pathway: break large molecules into smaller ones, release energy

Anabolic pathway: synthesize larger molecules from smaller one, uses energy

What is bioenergetics

the flow and transformation of energy

• carbohydrates —> glucose or stored as glucogen

• Proteins —> amino acids or excerted through urine

• Fats/lipids —> fatty acids or stored in adipose tissue

Describe cellular respiration

Involves nutrient molecules and O2 to convert into ATP and CO2

• Oxygen from breathing provides the O2 for input

• Glycolysis: Glucose —> Pyrvate, produces ATP and NADH

• Citric Acid Cycle (Kreb): purvate —> Ach-CoA, enter mitochondria, oxidizes to O2, forms ATP, NADH, and FADH

• Oxidative phosphorylation/ETC: strip electrons away to a lower energy, energy release creates hydrogen gradient —> movement of protons makes enerfy for ATP synthesize

Regulation of energy storage

• Glucose is stored as glucagon in liver and muscle. Excess —> fatty acids in adipose tissue

• Fatty acids are stored in adipose tissue

• Amino acids are stored as body proteins in muscle. Excess —> Glucose

Hormonal regulation of metabolism. How does insulin cause uptake? How does it benefit cellular respiration?

relies on endocrine system

Cell does not have a lot of glucose transporters naturally. Insulin causes activates intercellular pathways that inc the inseration of glucose transporters. Glucose can enter cell and be either stored as glycogen, broken down into pyurvate for ATP, or stored long term as fatty acid. BECAUSE GLUCOSE IS OUT OF THE BLOODSTREAM, THE BLOOD HAS DEC BLOOD GLUCOSE

Insulin

• Stimulus: inc blood glucose —> Beta cells in pancreas release insulin —> travel in blood —> target cells or cellular uptake —> dec blood glucose

• Insulin delivers glucose to the cell using glucose transporter. This is the ingredient for cells to use to start cellular respiration

Glucagon

• stimulus: low blood glucose —> alpha cells in pancreas release glucagon—> breakdown glycogen and releases glucose —> bloodstream —> target cells —> inc blood glucose

• Cellular respiration cannot happen without a constant supply of fuel (like glucose or fatty acids) to break down into ATP energy. Glucagon keeps cellular respiration supplied with fuel between meals and during sleep.

Type 1 and Type 2 diabetes

• caused by deficiency of insulin or dec response to insulin

• Type 1 diabetes: an autoimmune disorder (produce antibodies), immune system destorys pancreatic Beta cells, genetic predisposition

  • insulin shots

• Type 2: failure of target cells to respond to insulin (something wrong with insulin receptor or glucose insertion receptor), unable to uptake glucose, fat becomes main substrate

  • metaformin: reduces glucose production in liver, encourages uptake

  • Acarbose: inhibits enzymes that break carb into glucose, slow absorption

  • GLP-1: promote insulin release, promote satiety

What is the difference between an open and closed circulatory system? What is single and double circulation for closed circulatory? What is the advantages of a double circulation? Why do we oump blood twice through the heart?

Open

• circulatory fluid (hemolymph) bathes the organs directly

• no distinction btwn circulatory fluid and intersitial fluid

Closed

• blood is confined to vessels and is distinct from interstitual fluid

• chemical exchange happens btwn blood and intersititual fluid and fluid and cell

• Single circulation: One way flow, blood passes through the heart once per circuit

• Double circulation: blood passes through heart twice, separate gas exchange and systemic circuit

Advantages to double

• inc the pressure and flow rate

• important for larger bodies, high metabolic rate, high body temp (thermal homeostasis)

Why two pumps

• Capillaries create substantial resistance and pressure loss

• returning to the heart can restore pressure

What are arteries, veins, and capillaries?

Arteries: carry blood away from the heart, thicker wall to tolerate higher pressure

Veins: carry blood towards heart, valves prevent backflow

Capillaries: site of chemical exchange between blood and interstial fluid, one cell thick wall

What are the components are the heart - Atrium, Ventricle, valves, arteries

• Right Atrium: oxygen-poor blood enters from the vena cava

• Left atrium: oxygen-rich blood enters from pulmonary veins

• Right ventricle: oxygen-poor blood moves from R atrium to R Ventricle with valves

• Left ventricle: oxygen-rich blood moves from L atrium to L ventricle with valves

• Septum: thick muscular wall that divides the R and L sides

• Atrioventricular valve (AV) : separate A & V — tricuspid valve and bicuspid valve

• Semilunar valve: separate R &L ventricle from arteries

• Sup and Inf vena cava: carries oxygen-poor blood from tissues and pumps it into the R Atricum

• Pulmonary artery: carries oxygen -poor blood to lungs

• Aorta: carries oxygen rich blood from L ventricle to rest of body

*left ventricle is the thickest bc it needs to pump blood to all organs so it contracts with more force BUT both ventricles have the same amount of blood vol

Describe blood flow

Deoxygenated blood arrives from vena cava to R atrium —> tricuspid valve —> R ventricle —> Pulmonary semilunar valve —> pulmonary artery —> lung capillaries

Oxygenated blood arrives from pulmonary veins into L atrium —> bicuspid valve —> Left ventricle —> aortic semilunar valve —> aorta → arteries and capillaries —> rest of body

Why are valves important in blood flow?

prevent back flow and ensures blood is moving in the right direction

Valves open due to pressure differences

• pressure > behind valve = open

• pressure > infront of valve = close

Valves: AV and semilunar valves

What are the heart sounds you hear. what is a heart murmur

• “lub” (S1): caused by the closing of the AV valves (tri and bi), occurs at the oneset of ventricular systole, ventricular pressure > atrial pressure

• “dub” (S2): caused by closing of semilunar valves (aortic and pulmonary)

• heart murmur: defective valve function produces turbulent flow, can have back flow

What are the heart walls made out of

3 layers

• endothelium: inner layers, lines the heart

• Myocardium: cardiac muscle, middle layer

• Epicardium: external layer, covers the heart