Lecture 11 Neurons and Neural signals Flashcards Preview

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Flashcards in Lecture 11 Neurons and Neural signals Deck (40)
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1

Functions of the Nervous system

sensation
communication
integration
control

2

Neurons

functional cells of the nervous system
excitable cells- generate electrical signals (changes in membrane potentials)
communicate information in the form of electrical and chemical signals

3

Cell body of a neuron

contains the nucleus and most organelles

4

dendrites

branch from the cell body
receive signals from other cells through synapse

5

axon

extends from the cell body, conducts action potentials

6

axon hillock

region where axon joins the cell body

7

Trigger zone

initial segment adjacent to the axon hillock is the trigger zone for AP

8

axon terminals

contain vesicles with neurotransmitter, form synapses with other cells

9

Central Nervous system

brain and spinal cord
where most neurons are located

10

Peripheral Nervous System

Nerves, ganglia and sensory receptors
Afferent Division
Efferent Division

11

Afferent Division

Sensory neurons, input to CNS from sensory receptors
somatic sensory- from skin, muscles, bones & joints
Visceral sensory- from internal organs
Special senses- vision, hearing, equilibrium, olfaction, taste

12

Efferent Division

Motor neurons, output from CNS to effectors
Somatic Motor- to skeletal muscles (voluntary)
Autonomic (ANS) - to heart, smooth muscle, gland, adipose tissue (involuntary)
a.sympathetic
b. parasympathetic

13

Enteric Nervous System

Nerve network of the GI tract

14

Functional Types of Neurons

Sensory neurons
Motor neurons
Interneurons

15

Sensory Neurons

afferent
Input to CNS from sensory receptors; dendrites located at receptors, axon in nerves, cell bodies in ganglia outside the CNS

16

Motor Neurons

efferent
Output from CNS to effectors
cells bodies and dendrites located in the CNS, axons in nerves

17

Interneurons

communicate and integrate information within the CNS
located entirely within the CNS
Most common

18

Astrocytes

CNS
structural and chemical support, blood-brain barrier

19

Oligodendrocytes

CNS
Myelin in CNS

20

Microglia

CNS
Phagocytes

21

Ependymal cells

CNS
produce CSF

22

Schwann cell

myelin in PNS

23

satellite cells

in PNS ganglia

24

Graded Potentials

small, localized changes in membrane potential
formed at the cell body and dendrites
can be depolarization or hyperpolarization
spread passively and weaken with distance
size depends on stimulus strength
seen at cell bodies and sensory receptors
Stimulates action potentials
caused by opening of chemically gated channels
must exceed threshold to start AP

25

Action Potentials (nerve impulses)

large change in membrane potential
formed along the axon
rapid depolarization followed by repolarization
actively conducted along the axon
all or none- size is not dependent on stimulus strength
Doesn't weaken with distance

26

Phase 1 of action potentials

Rising (Depolarization) phase
-initial depolarization stimulus must be above threshold to form an AP
-voltage gated Na+ channels open
-activation gate opens in response to initial depolarization
-> rapid Na+ inflow -> rapid depolarization

27

Phase 2 of action potentials

Falling (repolarization) Phase
-Voltage gated Na+ channels close
inactivation gate - closes when depolarization reaches peak
-voltage gated K+ channels open
->rapid K+ outflow-> repolarization

28

Phase 3 of action potentials

Undershoot
voltage gated K+ channels remain open, high K+ permeability results in hyperpolarization
resting states of channels and resting potential restored at end of undershoot phase
-both voltage gates closed only the leak channels open when RP is restored

29

Name the properties of action potentials

threshold
all or more
regenerative
refractory period

30

Threshold

stimulus must be greater than a certain strength to evoke an AP
(subthreshold - cant start AP below threshold)
enough activation gates must open
-55mV