Fundamentals of Human Physiology

Chapter 7

Chapter 7

What are the main parts of a NEURON?

1. Dendrites → receives input

2. Cell body → integrates signals

3. axon hillock → trigger zone for stimulus

4. axon →transmits electrical signals

5. axon terminals → releases neurotransmitters

Define Afferent, Efferent and Interneurons

1. Afferent sensory: Carry info INTO CNS

2. Efferent motor: Carry info from CNS to muscle/gland

3. Interneurons: carry neurons within CNS

Describe the Flow of Information into a Neuron

Dendrites → Cell Body → Axon Hillock → Axon →Axon Terminals → Synaps 

Effect of Myelination on a Neuron

Increases speed of conduction by insulating axon → SALTATORY conduction = jumping from node to node

Different types of neurons and neuroglia cells IN THE CNS

• Astrocytes CNS: Support neurons, regulate ions and neurotransmitters, form blood-brain barrier

• Oligodendrocytes CNS: Myeline multiple axons in the CNS

• Microglia CNS: Immune defense, phagocytes of debris/pathogens

• Ependymal cells CNS: Line ventricles and spinal canal, produce cerebrospinal fluid

Different types of neurons and neuroglia cells in the PNS

• Schwann Cells: line the axon of a singular PNS axon

• Satellite cells: support and regulate environment around neuron cell bodies in ganglia

Compare neural regeneration in PNS vs CNS

• PNS: Schwann cells guide regrowth if the cell body is intact

• CNS: oligodendrocytes inhibits regrowth, scar tissue forms, very limited

How is an action potential produced?

Stimulus depolarizes membrane → reaches the -55mV threshold → Na+ channels open (depolarization) → Na+ RUSHES in and hits the peak → Na+ channels close, K+ channels open → K+ RUSHES out (repolarization) → hyperpolarization → returns to resting

Compare graded vs action potentials

• Graded: small, no threshold, no refractory period, located in dendrites or cell body, Ligated or mechanically gated, decay

• Action: all of none, large, long distance, triggered by a stimulus, depolarization followed by repolarization, must reach -55mV threshold, no summate, no decay, located in axon hillock, voltage gated Na+ or K+ channels

Characteristics of graded potentials 

Size varies, decays, short-distance, triggered by stimulus at dendrites/cell body, can summate

Characteristics of action potentials and conduction 

All or none, reach -55mV, long-distance, no decay, conducted via local current or saltatory conduction 

What is a refractory period

• The time when the axon is waiting for another AP

• Absolute: no new AP possible (Na+ channels inactivated

  • Depolarization and repolarization

• Relative: new AP possible, but needs stronger stimulus

  • End of depolarization and hyper polarization

Define depolarization, repolarization, overshoot, hyperpolarization

• Depolarization: inside becomes less negative due to Na+ channels rushing into cell 

• Repolarization: inside returning to near resting rate due to K+ channels opening

• Hyper polarization: When the membrane is more negative than the resting rate due to to make K+ leaving the cell

• Overshoot: inside becomes positive relative to the outside 

Describe Na+ and K_ permeability during an AP and how changes affect membrane potential

• Resting: High K+ permeability, low Na+, Stable potential 

• Depolarization: Voltage gated Na+ channels open → rapid Na+ influx → membrane potential rises

• Overshoot: Na+ influx continues until peak Na+ channels inactivate 

• Depolarization: K+ Channels open → K+ efflux → inside becomes negative again

• Hyper polarization:  K+ channels stay open briefly → membrane more negative than resting → channels close, return to resting potential 

Compare Na+ and K+ channel gating

• Na+ 2 gates (activation opens quickly, inactivation closes slowly) rapid response → rising phase of AP

• 1 gate, opens slowly after depolarization, delayed opening →. depolarization and hyper polarization 

What is the all-or-none principle

If threshold (-55mV) is reached, a full AP fires, if below the threshold- no AP, if above- AP same size

What is saltatory conduction

Conduction of myelinated axon: AP jumps from node to node where Na+ and K+ channels are concentrated. faster and more efficient

Compare electrical and chemical synapes

• Electrical: gap junctions, direct ion flow, very fast, reliable, less flexible, bidirectional

• Chemical: uses neurotransmitters, slower, flexible, excitatory or inhibitory 

Sequence of neural communication across a chemical synaps

1. AP arrives at pre synaptic terminal

2. Voltage-gated Ca2+ channels open → Ca2+ influx

3. Vesicles fuse with membrane → release neurotransmitters

4. neurotransmitters diffuse across cleft →bind to postsynaptic receptor

5. Ion channels open → postsynaptic potential

6. neurotransmitter is removed by reuptake, enzymatic break down or diffusion 

How is a neurotransmitter released from axon terminal

AP depolarizes terminal → Ca2+ channels open → Ca2+ influx → triggers vesicle fusion → neurotransmitter released → binds postsynaptic receptor → neurotransmitter cleared by reuptake, enzyme or diffusion

Excitatory vs Inhibitory postsynaptic potential

• EPSP: Ligated channels open allowing NA+ to enter

  • becomes less negative making it closer to threshold

• IPSP: Ligated channels open allowing Cl- or K+ to enter

  • Inside become more negative moving farther from threshold

Temporal vs Spatial summation

• Temporal: one presynaptic neuron fires rapidly over time

  • PSP builds up 

• Spatial: multiple presynaptic neurons fire at once

  • PSP combine, net effect decides threshold

Define a ligand-gated channel

Ion channel that opens when a neurotransmitter binds → fast synaptic transmission

Compare excitatory vs inhibitory neurotransmitters

• Excitatory: open CATION channels 

  • NA+ CA2+

• Inhibitory: open ANION channels 

  • CL- K+

Describe the role of Acetylcholinesterase

Enzyme that breaks down ACh in synaptic cleft → acetate + choline. Choline is recycled to make new ACh

How do G-Protien coupled receptors (GPCRS) produce synaptic potentials?

neurotransmitter binds to GPCRs → activates g-protien → g protein can beind to ion channels, activate second messenger 

Chapter 8

Chapter 8

How is the CNS protected

1. Bone: cranium encases brain, vertebral column surrounds spinal cord

2. Meninges

• Dura Mater: outermost, stronger

• Arachnoid Mater: middle, contain blood vessels

• Pia Mater: innermost, adheres to brain/spinal cord

3. CSF: cushions CNS, maintains chemical environment 

What is Cerebrospinal fluid (CSF)

• Produced by choroid plexuses in ventricles

• Functions

  • Buoyancy

  • Protection

  • Chemical stability

• Replaced 4 times a day

What are the 5 lobes of the cerebral context and their major functions

1. Frontal: voluntary movement, executive function, learning 

2. Parietal: somatosensory processing (touch, pressure, pain, temperature)

3. Temporal: Auditory processing, memory

4. Occipital: visual processing

5. Insula: taste, visceral sensation, emotion

How are sensory and motor areas organized in the cerebral cortex

• Motor: precentral gyrus, voluntary movement 

• Sensory: postcentral gyrus, touch, pressure, pain, temperature

Difference between right and life cerebral hemispheres

• left: dominate, language, analytical, math, logic

• Right: visual-spatial, patterns, music, art, reading maps

What are the methods to visualize the brain

1. CT scan: x-rays taken from different angles, good to detect brain bleeds, tumors, fracture, quick and widely available

2. MRI: uses magnetic fields ad radio waves to produce highly detailed images of brain, expensive, slow, not safe

3. fMRI: Measures blood flow changes that occur when neurons are active, map which brain areas are active during task, non-invasive, no radiation

4. PET scan: radioactive tracers to show where the brain is metabolically active, study cancer or alzheimers, radiation exposure 

5. EEG: electrodes placed on the scalp detect brain electrical signals, study brain rhythms, sleep,

Brocas area

Controls speech production, complex motor functions for speech

Wernickes area

Comprehension of language, formulate words, projects to brocas area

Aphasia

disturbance in comprehension and or expression of language

Brocas vs Wernickes aphasia

• Brocas- cant speak, can understand, cant respond

• Wernickes- can speak but with nonsense words, doesn’t understand

Types of memory and consolication

1. Short-term: <30 Sec

2. Long-term: >30 Sec

• non-declarative: skills, habits

• declarative: facts, events

• Consolidation: temporal lobes convert short-term to long-term; sleep needed

Function of thalamus

Relay station for sensory info, regulates consciousness, sleep, alertness

Function of hypothalamus

Maintains homeostasis: ANS regulation, endocrine control, body temp, circadian rhythms, emotions 

Midbrain structures and functions

• locations: upper portion of brainstep

• Tectum: superior colliculi (visual), inferior colliculi (auditory)

• Cerebral peduncles: connect cerebrum to brainstem/spinal cord

• Substantia nigra: dopamine, motor control

• Red nucleusL posture and motor coordination

• Functions: reflexes, motor coordination, relay motor signals

Function and components of brain stem

• Midbrain: reflexes and motor relay

• Pons: relay info, regulate breathing 

• Medulla oblongata: autonomic control

• Overal connects spinal cord and brain 

Function of cerebellum

• Coordination, posture, motor learning, timing movements

Ataxia

Uncoordnited movement due to cerebellar damage

Function of limbic system

Emotions, aggression, fear, smell, sex drive, goal-directed behavior 

Structure and function of reticular activating system

Network in brainstem projecting to cortext, arousal and wakefulness, proceses sensory info and affected by drugs 

Phases of sleep

• REM: dreaming, high brain activity, skeletal muscles inhibited, memory consolidation 

• NON-REM

  • Stage 1: light sleep

  • Stage 2: deeper, sleep spindles

  • Stage 3: deep sleep, delta waves

  • Stage 4: deepest, resorative

Ascending vs Descending tracts

Ascending: Sensory input to brain

Descending: motor output to body

Structure of spinal nerve

• Dorsal root- sensory

• Ventral root- motor

• dorsal root ganglion- sensory cell bodies

reflex arc pathways

Receptor → sensory neuron → integration (spinal nerves) → motor neuron → effector

Withdrawal reflex arc components

Pain receptor → sensory neuron → interneurons → motor neuron → flexor muscles → withdraw limb, crosses-extensor stabilizes opposite limb

Cranial nerves

1. Olfactory S: smell

2. Optic S: Vision

3. Oculomotor M: Eye movement

4. Trochlear M: eye movemnt

5. Trigeminal B: facial sensation, chewing

6. Abducens M: eye movement 

7. Facial B: expression, taste

8. Vestibulocochlear S: hearing/balance

9. Glossopharyngeal B: taste/ swallowing

10. Vagus B: autonomic, voice, taste, swallowing

11. Accessory M: sternoclinoidmastoid/ trapezius movement

12. Hypoglossal M: tongue movement 

Chapter 9

Chapter 9

Two division of the efferent division of the PNS

• somatic nervous system: voluntary control of skeletal muscles, singke neuron from CNS to muscle 

  • NT= ACh

• Autonomic nervous system: involuntary control of smooth, cardiac muscles, and glands. two neuron pathway

  • NT= Ach and norepinephrine

How is the autonomic nervous system subdivided

• Sympathetic: fight or flight, prepares body for stress

• Parasympathetic: rest and digest, conserves energy

Describe the organization of autonomic motor neurons

1. Preganglionic neuron: cell body in CNS, lightly myelinated axon to autonomic ganglion, ACh

2. Autonomic ganglion: relay station outside CNS

3. Postganglionic neuron: cell body in ganglion, unmyelinated axon to effector

   1. ACh-parasymp

   2. NE- symp

how does the number of neurons differ between somatic and autonomic pathways

• Somatic: 1 neuron CNS→effector

• Autonmic: 2 neurons CNS→ganglion→effector

where are the sympathetic preganglionic neurons located

Short axons, release ACh, synapse of sympathetic ganglia

Two types of sympathetic ganglia

• Sympathetic chain ganglia: run along side spinal cord

• Collateral ganglia: located in abdominal cavity near major arteries

Where are sympathetic post ganglionic neuron located and what do they release

In sympathic ganglia: long axons extend to effectors, typically release NE (except for sweat glands ACh)

How is the adrenal medulla related to the sympathetic nervous system

It acts as a modified sympathic ganglion. Preganglionic neruons release ACh directly onto adrenal medulla cells, which secrete epinephrine and norepinephrine into the blood

where are parasympathetic preganglionic neurons located

In the brainstem and sacral spinal cord

Parasympathetic preganglionic and post ganglionic neurons

Preganglionic neurons: long axons, release ACh, synapses in terminal ganglia near or in the effector

Postganglionic neurons: short axons, release ACh

What neuron trasnmitters are used in the ANS

• sympathetic: ACh (preganglionic), NE (postganglinoic), except sweat glands (ACh)

• Parasympathetic: ACh (both)

• Adrenal medulla: secretes epinephrine and norepiniphrine as hormones

Types of adregenic receptors and effects

1. Alpha 1: vasoconstriction, pupil dilation

2. Alpha 2: inhibit NE release

3. Beta 1: Increase heart rate and contractility

4. Beta 2: bronchodilation, vasodiliation in skeletal muscle

5. Beta 3: Lipolysis in adipose tissue

What are the effects of parasympathic nerce regulation

• Decreases heart rate

• Promotes digestion

• stimulates gland secretion

• constricts pupils

• contracts bladder

How does atropine affect parasympatheitc regulation

Block muscarinic ACh receptors, inhibiting parasympathing effects (increase heart rate, pupil dilation, reduced gland secretion 

Example of antagonistic actions between the sympathetic and parasympathetic 

Heart rate: sympathetic increase, parasympathetic decrease

Pupils: sympathetic dilates, parasympaethic constricts 

Example of cooperative actions between the sympathetic and parasympethic 

Reproductive system: parasymp promotes erection, symp promote ejaculation 

CHAPTER 10!

CHAPTER 10!

what is sensory trasnduction

The process of converting a physical stimulus into an electrical signal

Phasic Receptors

Rapidly adapting receptors that respond only at the onset or offset of a stimulus

Receptor Potential

A graded electrical change in a receptor cell’ its size depends on a stimulus strength and determines how often action potential fire

Differentiate between sensation and perception

• sensation: detection of stimulus 

• perception: brains interpretation and meaning of the sensation

Sensory acuity

Precision in detecting/localizing a stimulus

What factors affect acuity

Receptive field size, lateral inhabitation, and convergence

Five types of sensory receptors

1. mechanorecpetors: physical forces such as pressure, touch, vibration,

2. thermoreceptors; change in temperature

3. photoreceptors: detenct light, allow vision

4. chemoreceptors: deteect chemical stimuli such as taste, smell, blood pH, O2 and Co2 levels

5. nociceptors: pain

What neurotransmitters transmit pain

Substance P and glutamte

What are the five taste modalites

1. sweet

2. sour

3. salty

4. bitter

5. umami

how is taste converted to the brain

via carnial nerve 7 (facial), 9 (gloccopharyngeal),  and 10 (vagus) → brainstem → thalamus → gustatory cortext

How do ordorant molecules stimulate receptors

They dissolve mucus, bind to olfactory receptor proteins, open ion channels and send signals via the olfactory bulb → olfactory cortex and limbic system

What does frequency of a sound wave determine

PITCH!

what does amplitude determine

LOUDNESS

What is Hertz (Hz)

Unit of frequency= cycles per second

What are they parts of the vestibular apparatus

Semicircular canals (rotation)

Utricle and saccule (linear acceleration and gravity)

what are the otolithc organs

• Utricle- horizontal acceleration

• Saccule- vertical accelration

  • Containing hair cells with otolith crystals 

vestibular pathways

hair cells → cestibular nerve → vestibulocochlearnerce (8) → brainstem → cerebellum and cortext

how does basilar membrane movement cause hearing

Vibrations bend hair cells in organ of corti → ion channels open → depolarization → action potential in cochlear nerve → brain interprets sound

How is loudness discriminated

by amplitude (greater hair cell bending= more AP

How is pitch discriminated

By which part of the basliar membrane (base=high pitch, apex= low pitch)

what is the neural pathway of hearing

Hair cells → cochlear nerve → cochlear nuclei → inferior colliculus → thalamus → auditory cortex

what structures focus light onto the retina

Cornea and lens (refraction)

What is refraction

Bending of light rays as they pass between media or different densities

what is accommodation and how does it work

Adjusting lens shape to focus on near vs far objects

• near = clilary muscles contract, lens thickens

• far = muscles relax, lens flattens

common eye disorders

• myopia: near-sighted

• hyperopia: far- sighted

• astigmatism

• glaucoma

• cataracts

structure of retina

Rods and cones → bipolar cells → ganglion cells →optic nerve

Dark adaptiation

Rods regian sensitivity, rhodospin regenerates

Light adaptation

Robs bleach, cones take over

How does light affect synaptic activity in ret?

Dark: photreceptors release glutame → inhibit bipolar cells

Light: les glutamte → bipolar cells activate ganlion cells → APS