Compendium 8 - How do we control ourselves

Question 1

what are the 5 functions of the nervous system

Answer 1

1. receive sensory input
2. integrate information
3. motor output
4. maintaining homeostasis
5. establish and maintain mental activity

Question 2

what are 6 differences between the somatic and autonomic pathways

Answer 2

s= voluntary control
a= involuntary control

s= controls skeletal muscles
a= controls smooth muscle, cardiac muscle, glands

s= single neuron
a= 2 neurons

s= cell body in CNS
a= cell body (of second neuron) in ganglion

s= myelinated
a= preganglionic is myelinated and postganglionic is unmyelinated

s= stimulation only
a= stimulation or inhibition

Question 3

where do you find enteric neurons

Answer 3

in the walls of the GI tract

Question 4

what are the functions of the enteric nervous system

Answer 4

• stimulate + inhibit muscle contraction and gland secretion
• detect change in content of lumen

Question 5

what are 2 factors the distinguish the sensory and motor pathways

Answer 5

sensory = afferent and motor = efferent
s= has a dorsal root ganglion
m= cell bodies inside CNS

s= from receptor to CNS
m= from CNS to effector

Question 6

what regions of the spinal cord do the sympathetic and parasympathetic nervous systems originate

Answer 6

sympathetic= thoracolumbar region
parasympathetic= craniosacral region

Question 7

what are the 3 structural classifications of neurons and where can you find them

Answer 7

multipolar - motor neuron pathways
bipolar - eye and nasal cavity
pseudounipolar - sensory neuron pathways

Question 8

what division of peripheral NS has an interneuron and which does not

Answer 8

autonomic has not got an interneuron
somatic has an interneuron

Question 9

what 2 parts make up the trigger zone in a neuron

Answer 9

axon hillock and initial segment

Question 10

what is the structure(2) and function(4) of Astrocytes

Answer 10

Structure:
- star shaped, end feet wrapped around BVs and neurons

Function:
- support + scaffold
- control blood-brain barrier permeability
- homeostasis in CNS
- form glial scar tissue

Question 11

What is the structure(2) and function(2) of Ependymal cells

Answer 11

Structure:
- line ventricles of brain and central canal of spinal cord
- have cilia
Function:
- production and release of CSF
- cilia circulate CSF

Question 12

What is the structure and function(2) of Microglial cells

Answer 12

• can be resting or active

Function:
-when active they become mobile and phagocytic in response to inflammation
- target foreign substances, necrotic tissue (dead cells) and pathogens

Question 13

What is the structure(2) and function(2) of oligodendrocytes

Answer 13

Structure:
- cytoplasmic extensions wrap axons
- 1 cell can wrap around multiple axons

Function:
- form myelin sheath
- insulation of CNS axons

Question 14

What is the structure(2) and function(1) of Schwann cells

Answer 14

Structure:
- cytoplasmic extensions wrap around axon forming myelin sheath
- cell forms part of sheath

Function:
- insulation of PNS axons

Question 15

What is the structure(1) and function(2) of Satellite cells

Answer 15

Structure:
- surround cell bodies in ganglia (in sensory and autonomic pathways)

Function:
- provide support and nutrition
- protects from heavy metal poisoning

Question 16

what structures are found in grey matter and white matter

Answer 16

Grey matter: neuron cell bodies, dendrites, axon terminals, ganglia, unmyelinated axons, glial cells, synapses

White matter: very few cell bodies, myelinated axons

Question 17

what are the typical concentrations of k+ and Na+ ions inside and outside the cell (at -70 RMP)

Answer 17

K+: intracellular = 148, extracellular = 5
Na+: intracellular = 10, extracellular= 142

Question 18

what are the types of gated ion channels

Answer 18

ligand-gated: chemical attachment
voltage-gated: difference in charge
other: temperature, pressure, touch

Question 19

what are the comparative amounts of K+, Cl- and Na+ channels in a membrane

Answer 19

more K+ and Cl- than Na+

Question 20

what is the refractory period and what are the two parts

Answer 20

it is the time taken to reestablish RMP, where another action potential cannot occur
Absolute: no amount of stimulus can trigger and action potential
Relative: if the stimulus is very strong it will generate

Question 21

describe the 5 steps in an action potential crossing a synapse.

Answer 21

1. action potential arrives and causes Ca2+ channels to open
2. Ca2+ diffuse in and cause exocytosis of vesicles containing neurotransmitters
3. neurotransmitters are released and diffuse across the synaptic cleft
4. neurotransmitters combine with receptors and cause ligand-gated Na+ channels to open in postsynaptic membrane
5. Na+ diffuse into postsynaptic membrane causing depolarisation of the next neuron.

Question 22

what 3 things can happen to a neurotransmitter after it has done its job

Answer 22

• reabsorbed by presynaptic terminal
• broken down by enzymes
• diffuse far away into the extracellular matrix

Question 23

what happens to the Acetylcholine neurotransmitter after its done

Answer 23

it splits into choline and acetic acid, the choline is taken up by presynaptic terminal again and is used to make another neurotransmitter

Question 24

what are 7 characteristics of reflexes

Answer 24

• Automatic (not higher brain involvement)
• homeostatic (doesn’t require mental processing)
• somatic or autonomic
• rapid
• predictable
• unlearnt
• simplest do not have interneurons

Question 25

what are 5 characteristics of a reaction

Answer 25

• voluntary
• initiated by sensory stimulus
• relatively slower than a reflex
• involves brain and spinal cord
• reaction improved through repetition

Question 26

what are 4 types of reflexes

Answer 26

• somatic - protects from harm (with skeletal muscle)
• autonomic - maintains body functions (with smooth muscle)
• monosynaptic - no interneuron
• polysynaptic - have an interneuron