The Nervous System

Question 1

What is the nervous system?

Answer 1

-The nervous system is a complex network of nerves and cells
that carry messages to and from the brain and spinal cord to
various parts of the body

-The nervous system includes both the central nervous
system and peripheral nervous system

Question 1

What is the central nervous system?

Answer 1

Brain and spinal cord
· Integrates, processes and coordinates sensory data and motor commands

Question 1

What is the peripheral nervous system?

Answer 1

(nerves that aren’t in our brain and spinal cord)
· Neural tissue outside CNS
· Delivers information to CNS
· Somatic nervous system – voluntary & involuntary (automatic)
· Autonomic nervous system
→ Sympathetic
→ Parasympathetic
Cells types are neurons and neuroglia

Question 1

Are motor neurons afferent or efferent?

Answer 1

They are efferent

Question 1

Are sensory neurons afferent or efferent?

Answer 1

They are afferent

Question 1

What are dendrites?

Answer 1

Dendrites extend out from cell body, highly branched, neurons receive info from other neurons at the dendrites, large surface area

Question 2

What are schwann cells

Answer 2

Form the myelin sheath insulating and protecting the axon

Question 2

What are axons?

Answer 2

long cytoplasmic process, propagates an action potential

Question 2

What are Telodendria?

Answer 2

terminal branches or synaptic terminals

Question 2

What is the myelin sheath?

Answer 2

The insulating envelope of myelin that surrounds an axon and facilitates the transmission of nerve impulses

Question 3

What are nodes of Ranvier?

Answer 3

A gap in the myelin sheath of a nerve, between adjacent Schwann cells

Question 4

What is an action potential?

Answer 4

Action potential is a short-lasting event in which the membrane potential of a neuron rapidly rises and falls

Question 5

How is an action potential generated?

Answer 5

• Voltage gated sodium and potassium channels on the membrane (resting potential of -70mV)
• Threshold is -55mV
• Na channels open and flow by the electrochemical gradient because it is positively charged the membrane potential increases to +30 mV
• Na channels close and K channels open
• K leaves the cell
• Repolarisation -70mV, K channels close

Question 6

Role of the Na and K pump?

Answer 6

-In an AP, depolarisation results from an influx of Na ions
-Repolarisation results from the loss of K ions
The Na/K exchange pump returns intracellular & extracellular ion levels back to resting levels
-Pump requires ATP

Question 7

What is continuous conduction?

Answer 7

-Non-myelinated neurons- just the axon
-Slow process
-AP moves by continuous propagation down the axon
-Depolarisation spreads from one adjacent region to the next

Question 8

What is saltatory conduction?

Answer 8

Myelin limits movement of ions across the membrane
AP ‘jumps’ from one node of Ranvier to the next
Fast process

Question 9

What is the effect of the axon diameter?

Answer 9

A thicker axon means more cytoplasm
Axon diameter, as well as presence of myelin, speeds up the process.
This is because, cytoplasm shows less resistance to ion movement than plasma membrane
Therefore in larger axons the depolarisation moves along more quickly

Question 10

What is a synapse?

Answer 10

A gap between two neurons.

Question 11

What events take place at the synapse?

Answer 11

• Acetylcholine (ACh) is the most common neurotransmitter
• Excitatory neurotransmitter
• Causes depolarisation and propagation of AP
• Inhibitory neurotransmitter
• Causes hyperpolarisation and suppression of AP
• Cholinergic synapse (where we get ACh)
• Acetylcholinesterase breaks it down to aloow the receptor to be inactivated and used again

Question 12

What is a monosynaptic reflex?

Answer 12

-Stretch reflex
-No interneuron, sensory neurons act directly on motor neuron in spinal cord
-Fast response
-Patellar reflex

Question 13

What is a polysynaptic reflex?

Answer 13

Produce more complex responses
Interneurons can control motor neurons in several muscle groups simultaneously

Question 14

Brain- What is the function of the meninges?

Answer 14

tough, fibrous, this and CSF provide a cushion for the brain inside the skull

Question 14

Brain-What is the medulla?

Answer 14

involuntary functions, contains the cardiac, respiratory, vomiting and vasomotor centres and therefore deals with the autonomic (involuntary) functions of breathing, heart rate and blood pressure. Cannot live without it

Question 15

Brain- What is the Pons?

Answer 15

Relays messages from forebrain to cerebellum, involved in sleep, respiration, hearing, taste, eye movement etc

Question 16

Brain- What is the cerebrum?

Answer 16

largest part of the human brain, associated with higher brain function such as thought and action.

Question 17

Brain- What is the cerebellum?

Answer 17

coordinated muscular activity at subconscious level

Question 18

Brain- What is the function of the midbrain?

Answer 18

regulates auditory and visual reflexes

Question 19

Brain- What is the thalamus?

Answer 19

relay motor and sensory signals to the cerebral cortex

Question 20

Brain- What is the hypothalamus?

Answer 20

control hormone production and body temp

Question 21

What is the automatic nervous system?

Answer 21

Responsible for control of the bodily functions not consciously directed, such as breathing, heartbeat and digestive processes

Question 22

What are sympathetic neurones?

Answer 22

-They produce a ‘Fight or flight’ response
-Constantly active at a basic level to maintain homeostasis
-Uses energy and increases metabolic rate
-Noradrenaline released at NMJ
-Dilate pupils, heart rate increases, skeletal muscle blood vessels dilate, GIT blood vessels constrict

Question 23

What are parasympathetic neurons?

Answer 23

-‘Rest and digest’ response
-Conserves energy and lowers metabolic rate
-ACh released at NMJ
-Constriction of pupils, secretion by digestive glands, secretion of hormone, increase in smooth muscle activity of GIT, reduction in heart rate
-Complementary to sympathetic system