Nervous system (16)

Question 1

What are the 3 parts of the nervous system?

Answer 1

1) Sensory input- NS uses millions of sensory receptors to monitor changes occurring both inside and outside of the body. Gathered info is called sensory input
2) Integration- NS processes and interprets sensory input and decides what should be done at each moment
3) Motor output- NS activates effector organs (muscles and glands) to cause a response (motor output)

Question 2

What are the 3 functions of the NS?

Answer 2

1) To monitor internal and external environments
2) Process info
3) Direct body processes and behaviours

Question 3

What is the CNS?

Answer 3

> Brain and spinal cord
The integrating and control centre of the NS
Interprets sensory input and dictates motor output based on reflexes, current conditions and past experience

Question 4

What is the PNS?

Answer 4

> Part of the NS outside the CNS
Consists mainly of nerves that extend from the brain and spinal cord
Spinal nerves- carry impulses to and from the spinal cord
Cranial nerves- carry impulses to and from the brain
Communicates between the CNS and the rest of the body

Question 5

What are the 2 divisions of the PNS?

Answer 5

1) Sensory (afferent) division- somatic (from skin, skeletal muscles and joints) and visceral (from visceral organs ) nerve fibres. Conducts impulses from receptors to CNS
2) Motor (efferent) division- carries impulses from CNS to effector organs (muscles and glands). Uses motor fibres

Question 6

What are the 2 divisions of the motor division?

Answer 6

1) Somatic- voluntary motor fibres; conducts impulses from CNS to skeletal muscle; reflexes
2) Autonomic- Visceral (involuntary) motor nerve fibres; conducts impulses from CNS to cardiac muscle, smooth muscle and glands

Question 7

What are the 2 divisions of the autonomic system?

Answer 7

1) Sympathetic- Mobilises body systems during activity ; ‘fight or flight’
2) Parasympathetic- conserves energy; promotes “housekeeping” functions during rest; ‘rest and digest’

Question 8

What is nervous tissue?

Answer 8

> NS consists mostly of nervous tissue, which is highly cellular
Less than 20% of CNS is extracellular space meaning that the cells are tightly packed and intertwined with each other

Question 9

What are neurones?

Answer 9

Nerve cells that are excitable (respond to stimuli by changing their membrane potential) and transmit electrical signals

Question 10

What are neuroglia?

Answer 10

> Supporting cells that surround and wrap the more delicate neurones
Have branching extensions and a cell body
Smaller than neurones, outnumber them 10:1 and make up about half the mass of the brain
6 types- 4 in CNS and 2 in PNS
In CNS- astrocytes, microglial cells, ependymal cells and oligodendrocytes
In PNS- Satellite cells and Schwann cells

Question 11

What are the functions of neuroglia?

Answer 11

1) Provide a supportive scaffolding for neurones
2) Segregate and insulate neurones
3) Guide young neurones to their proper connections
4) Promote health and growth

Question 12

What are the characteristics of neurones?

Answer 12

1) Excitable- respond to stimuli, produce and conduct electrical impulses, release chemical regulators (neurotransmitters)
2) Amitotic- Cant take place in mitosis so cannot reproduce themselves
3) Long lived
4) High metabolic rate- lots of mitochondria

Question 13

What is the structure of the neurone?

Answer 13

1) Dendrites- receives messages from adjacent cells
2) Cell body- Contains all the biochemical machinery (organelles) necessary to keep the neurone alive and do its job
3) Axon- transmits messages in the form of neurotransmitters away from the cell body to other neurones, muscles or glands
4) Myelin sheath- surrounds the axon; layer of fatty material derived from neuroglial cells; prevents electrical signals from adjacent cells interfering with each other; speeds up production of nervous impulses

Question 14

What is neurotransmission?

Answer 14

> Neurotransmitters travel from one neurone to another
Changes in ion conc. occur in the sending neurone’s cell membrane
2 types- excitatory and inhibitory

Question 15

What are excitatory and inhibitory impulses?

Answer 15

Excitatory- The probability that the receiving neurone will fire increase
Inhibitory- The probability that the receiving neurone will fire decreases

Question 16

What are some examples of neurotransmitters?

Answer 16

> Acetylcholine- shortage of this is associated with Alzheimer’s (excitatory)
Dopamine- The degeneration of brain cells that produce dopamine tends to cause Parkinson’s disease (inhibitory)
Serotonin- Low levels of serotonin associated with insomnia, depression, anorexia nervosa, SAD
GABA- associated with depression, stimulated by diazepam

Question 17

What are some examples of diseases of the CNS?

Answer 17

> Multiple sclerosis 
> Alzheimer's disease
> Parkinson's disease
> Cerebro-vascular disease 
> Hydrocephalus

Question 18

What are the protections of the brain?

Answer 18

> Hair
Scalp
Cranium
3 layers of the meninges (lining of the brain)
Ventricles filled with cerebral spinal fluid (CSF)

Question 19

What are the 3 meninges?

Answer 19

1) Dura mater
2) Arachnoid matter
3) Pia matter

Question 20

What is cerebrospinal fluid?

Answer 20

Formation- choroid plexus and walls of the ventricles
Circulation- Around the brain and spinal cord and the arachnoid villi reabsorb it
Functions- mechanical shock absorber; chemical protection; nourishment of meninges
Lumbar puncture- collection of CSF where needle is inserted into spinal canal

Question 21

What is the blood-brain barrier?

Answer 21

> A very specialised physical barrier system of endothelial cells that separates the blood from the underlying brain cells, protecting the brain cells, preserving brain homeostasis
The brain endothelium has a complex arrangement of tight junctions between the cells that restricts the passage of molecules

Question 22

What are the cranial nerves?

Answer 22

> Set of 12 paired nerves that arise directly from the brain
The first 2 (olfactory and optic) arise from cerebrum, remaining 10 emerge from brain stem
Numbered in roman numerals

Question 23

What are spinal nerves?

Answer 23

> Mixed nerves which carry motor, sensory and autonomic signals between the spinal cord and the body
31 pairs of spinal nerves, one of each on each side of the vertebral column
8 pairs of cervical nerves (C1-C8)
12 pairs of thoracic nerves (T1-T12)
5 pairs of lumbar nerves (L1-L5)
5 pairs of sacral nerves (S1-S5)
1 pair of coccygeal nerves (Co 1)