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

Action Potential

• long distance

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

• does not decay

• absolute refactory and relative refactory period

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 (ESPs): 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

• 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

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 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