nervous tissues

Question 1

what is the function of the nervous system?

Answer 1

to provide rapid precise communication between different parts of the body via the action of neurones (carry info throughout body via electric impulses)

Question 2

what are the two main divisions of the nervous system?

Answer 2

central nervous system and peripheral nervous system

Question 3

what makes up the central nervous system?

Answer 3

the brain and spinal cord

Question 4

what makes up the peripheral nervous system?

Answer 4

the nervous tissue out- with the CNS

Question 5

what is the role of the PNS?

Answer 5

to deliver sensory info to the CNS where it’s processed and sent back out to the PNS where signal responses are sent out from

Question 6

what are the two functional divisions of the PNS?

Answer 6

• somatic NS
• autonomic NS

Question 7

what is the role of the somatic NS?

Answer 7

regulates voluntary control of skeletal muscle

Question 8

what is the role of the autonomic NS?

Answer 8

controls unconscious functions

Question 9

what are the two divisions of the autonomic NS?

Answer 9

• parasympathetic
• sympathetic
• both of these can regulate our smooth and cardiac muscle contractions

Question 10

describe the role of the parasympathetic NS

Answer 10

‘rest and digest’ division which regulates less urgent processes such as digestion etc.

Question 11

describe the role of the sympathetic NS

Answer 11

‘fight or flight’ division which responds when our body needs immediate action

Question 12

what are the cells of the nervous system?

Answer 12

neurons and (neuro)glial cells

Question 13

describe neurons

Answer 13

nerve cells which are the functional units of the nervous system and send signals around the body

Question 14

describe (neuro)glial cells

Answer 14

support cells which protect, support and provide nutrients and immune functions to the neurones

Question 15

what are neurons specialised for?

Answer 15

intercellular communication

Question 16

describe neurons

Answer 16

• long lived
• high metabolic rate
• contain dendrites, cell body, single axon, terminal boutons
• all neaurons have excitability

Question 17

what does ‘excitability’ in neurons mean?

Answer 17

a difference in charge between the inside and outside of the cell to allow the generation of action potentials

Question 18

what are dendrites?

Answer 18

highly branched processes extending from the cell body
- they form synapses with adjacent neurons
- the respond to external stimuli from other neurons
- they convey incoming info to the cell body, where it is interpreted

Question 19

describe the cell body of a neuron

Answer 19

• large
• contains a large nucleus and prominent nucleolus (sign of neurons high metabolic demand)
• located in the CNS
• nissil bodies (clusters of RER giving the granular look and grey matter)
• numerous mitochondria
• stain dark
• rich in organelles
• axon hillock is a specialised part of the cell body which connects to the axon
• the cell body can also be called the perikaryon

Question 20

describe the axon

Answer 20

-rapidly propagates signals from cell body towards axon terminals
- specialised to conduct action potentials
- in PNS either non-myelinated or myelinated
- in CNS they are all myelinated

Question 21

what kind of matter does myelin give?

Answer 21

white matter

Question 22

describe terminal boutons

Answer 22

-form synapses with other neurons or effector organs
- neuromuscular junctions
- where electric signals are converted to chemical signals
- where neurotransmitters are released and convey messages to the next cell in the pathway

Question 23

what would the effector organ be for a motor neuron?

Answer 23

skeletal muscle

Question 24

what is the function of (neuro) glia cells?

Answer 24

to protect and support neurons

Question 25

how much of the total mass of the CNS do glia cells form?

Answer 25

almost 50%

Question 26

name the types of neuroglia cells in the CNS

Answer 26

-ependymal cells - astrocytes - microglia - oligodendrocytes

Question 27

name the types of neuroglia cells in the PNS

Answer 27

- satellite cells - shwann cells

Question 28

describe CNS ependymal cells

Answer 28

- simple ciliated cuboidal epithelium tightly bound - line fluid- filled cavities in the brain (ventricles) and spinal cord - no basement membrane so instead, cells taper into loss processes which merge with underlying tissues - various cilia and microvilli which help move and regulate composition of spinal fluid

Question 29

describe CNS astrocytes

Answer 29

- named after their star shape - large glial cells - most numerous support cell in CNS - highly branched (packed into spaces between neurons) - provide mechanical support and mediate the exchange of metabolites between neurons and the vascular system - from the blood-brain barrier - regulate the chemical environment

Question 30

describe CNS microglia cells

Answer 30

- named due to small size - phagocytic capacity - derived from monocytes and macrophages - transform into large phagocytic cells in response to tissue damage - remove invading microbes and dead cells from CNS

Question 31

describe CNS oligodendrocytes

Answer 31

- function to myelinate axons - form myelin sheaths around all CNS axons - provide structural and metabolic support - single oligodendrocytes can myelinate up to 50 axons - any one axons requires numerous oligodendrocytes to myelinate it

Question 32

describe PNS satellite cells

Answer 32

- cells not in CNS are located in structures called ganglions - flattened cells which cover the surface of neuronal cell bodies - provide structural and functional protection

Question 33

what are ganglions?

Answer 33

structures which cells out with CNS are located- aggregations of nueronal cell bodies located near spinal cord

Question 34

describe PNS Shwann cells

Answer 34

- form myelin sheaths around PNS axons - provide structural and metabolic support - non-myelinated axons (smaller) are enveloped in Shwann cells cytoplasm - myelinated axons (larger) are gradually wrapped by the Shwann cell membrane to create a myelin sheath

Question 35

what is the function of myelin sheaths in the NS?

Answer 35

- allow electrical impulses to transmit quickly and efficiently along nerve cells - increase rate of action potential