Physiology Exam 2 Study Guide

What are the two major divisions of the nervous system?

CNS = brain and spinal cord

PNS = all nerves outside the CNS

What is the difference between afferent and efferent neurons?

Afferent = sensory —> CNS

Efferent = CNS —> Effector

What are the functions of each part of the neuron?

• Dendrites = receive signals

• Soma = integrates signals

• Axon hillock = starts AP

• Axon = conducts AP

• Axon terminal = releases neurotransmitter

Where are the leak channels found and what do they do?

Cell membranes; always open and help establish the resting membrane potential

Where are ligand-gated channels found?

Dendrites and cell body

Where are voltage-gated Na+ and K+ channels found?

Axon hillock and axon

Where are voltage-gated Ca2+ channels found?

Axon terminals

What is the resting membrane potential of a neuron?

-70 mV

What mainly causes the resting membrane potential?

K+ leak channels

What does the Na+/K+ pump do?

Moves 3 Na+ out and 2 K+ in

What is the difference between the Nernst and GHK equations?

Nernst = one ion

GHK = multiple ions and permeability

What are graded potentials?

Small local membrane potential changes that can summate

What triggers an AP?

Threshold is reached at the axon hillock

What causes depolarization?

Na+ channels open —> Na+ enters

What causes repolarization?

K+ channels open —> K+ leaves

What causes hyperpolarization?

K+ channels close slowly

What is the absolute refractory period?

No second AP can occur

What is the relative refractory period?

A stronger stimulus is needed to fire another AP

What factors increase AP potential conduction speed?

• Myelin

• Larger axon diameter

• Higher temperature

How does myelin speed conduction?

Saltatory conduction between Nodes of Ranvier

Chemical vs. Electrical synapse

Chemical = neurotransmitters

Electrical = gap junctions

Steps of chemical synaptic transmission

AP —> Ca2+ enters —> ACh released —> receptor binds —> response

Ionotropic vs. Metabotropic receptors

Ionotropic = fast, ligand-gated

Metabotropic = slow, GPCR

What is an EPSP?

Depolarization; neuron more likely to fire

What is an IPSP?

Hyperpolarization; neuron less likely to fire

Opening Na+ channels causes what?

Depolarization (EPSP)

Opening K+ channels causes what?

Hyperpolarization (IPSP)

Opening Cl- channels causes what?

Hyperpolarization (IPSP)

Convergence vs. Divergence

Convergence = many —> one

Divergence = one —> many

Presynaptic facilitation vs. inhibition

Facilitation = increase in NT release

Inhibition = decrease in NT release

What is long-term potentiation (LTP)?

Strengthening of synapses after repeated stimulation

Why is LTP important?

Learning and memory

Function of astrocytes?

Support neurons and help form the blood-brain barrier

Function of oligodendrocytes?

Produce CNS myelin

Function of Schwann cells?

Produce PNS myelin

Function of microglia?

Immune defense (phagocytosis)

Function of ependymal cells?

Produce and circulate CSF

Function of the blood-brain barrier?

Protects the brain and regulates what enters

Five parts of a reflex arc?

Receptor —> afferent neuron —> integration center —> efferent neuron —> effector

Three functional areas of the cerebral cortex?

Sensory, motor, association

What do multimodal association areas do?

Integrate information from multiple senses

Function of the frontal lobe?

Planning, movement, and speech

Function of the parietal lobe?

Somatosensory processing

Function of the temporal lobe?

Hearing and language comprehension

Function of the occipital lobe?

Vision

Function of the cerebellum?

Balance and coordination

Broca’s vs. Wernicke’s aphasia?

Broca’s = can’t produce speech

Wernicke’s = can’t understand language

Sympathetic vs. Parasympathetic

Sympathetic = fight or flight

Parasympathetic = rest and digest

What is dual innervation?

Both ANS divisions innervate the same organ

Antagonistic vs. tonic control

Antagonistic = opposite effects

Tonic = one division changes activity

Neurotransmitter released by all preganglionic neurons

Acetylcholine (ACh)

Receptor on all autonomic ganglia?

Nicotinic

Parasympathetic postganglionic neurotransmitter and receptor?

ACh —> muscarinic

Sympathetic postganglionic neurotransmitter and receptor?

NE —> adrenergic

Alpha-1 receptor effects?

Vasoconstriction, pupil dilation, urinary retention

Alpha-2 receptor effects?

Decreases NE release

Beta-1 receptor effects?

Increases heart rate and contractility

Beta-2 receptor effects?

Bronchodilation and vasodilation

Agonist vs. antagonist

Agonist = activates receptor

Antagonist = blocks receptor

Why does an alpha-2 agonist lower blood pressure?

It decreases NE release, reducing alpha-1 stimulation

Steps of the neuromuscular junction?

AP —> Ca2+ enters —> ACh released —> ACh binds receptor —> Na+ enters —> Muscle AP —> ACh broken down