The Nervous System Flashcards
1
Q
The nervous system is Divided into two parts
A
- Central nervous system-Main unit and connected to the rest of the body
- Peripheral nervous system-Carries information to and instructions from the brain
2
Q
- Nervous tissue is composed of
A
- Nerve cells – neurons
- Contain fibres which transmit nerve impulses
- Neuroglia– connective tissue
which supports neurons - Only found in the nervous system
- Does not transmit nerve impulses
3
Q
what are Neurons
A
- Basic units of the nervous system
- Long and narrow cells– up to 1m
- Easily damaged by toxins and lack of oxygen
- Not usually replaced when they die
- Some may have the ability to regenerate
4
Q
Neurons composed of
A
- Cell body
- Centre of the neuron. Contains the nucleus, cytoplasm and organelles e.g. mitochondria
- Dendrites
- Nerve fibres. Transmit nerve impulses TO the cell body
- Most neurons have several dendrites
- Axon
- A long single nerve fibre
- Transmits nerve impulses AWAY from the cell body
- Neurons generally have one axon
5
Q
what is * Myelin sheath
A
- Made of a white, fatty substance which covers the axon
- Protects it from pressure and helps speed up nerve conduction
6
Q
what is * Neurilemma
A
- A fine delicate membrane which surrounds the myelin sheath and helps regenerate nerve cells
- Composed of the cytoplasm and the nuclei of the Schwann cells which lie outside the myelin sheath
- Only found in the peripheral nervous system
7
Q
what are Nodes of Ranvier
A
- Gaps in the myelin sheath along the nerve
- Speed up the passage of nerve impulses along the fibre
8
Q
what are * Synapse
A
- A point where one neuron meets another
- Chemical messenger fills the gap and enables the impulse to be transmitted
9
Q
- End feet/axon terminals
A
- Ends of the fibrils that make the axon more expanded
- Pass on the impulse from the axon to the dendrites of the next neuron
10
Q
Types of neurons – by function
A
- Sensory neuron – afferent neurons
- Transmit impulses to the CNS so it can be processed
- Motor neuron – efferent neurons
- Transmit impulses to muscles, organs and glands
- Interneuron – found only in the CNS
- Connect one neuron to another
11
Q
Types of neurons – by structure
A
12
Q
basic Function of Neurons
A
- Receive signals (or information).
- Integrate incoming signals (to determine whether or
not the information should be passed along). - Communicate signals to target cells (other neurons or
muscles or glands).
13
Q
all Nerves and nervous tissue
A
14
Q
The nerve impulse – action potential
A
- Nerve cells transmit and receive nerve impulses throughout the body
- Impulses are created in response to internal or external stimuli
- Temperature, pressure, chemicals
15
Q
Resting membrane potential
A
- Positively charged sodium and potassium ions are present inside and outside the cell
- In a resting axon
- The concentration of sodium ions is lower inside the cell
- The concentration of potassium ions is higher inside the cell
- Due to
- Sodium potassium pump
- Many leakage channels for potassium
- Few leakage channels for sodium
- Result
- Inside of cell is more negative than the outside
- Chemical gradients for Na+ and K+ are created
16
Q
Sensory receptors – AP generation
A
- Stimuli are detected by sensory receptors
- The axon becomes temporarily more permeable to sodium ions which rush in
- The inside of the cell becomes more positive – depolarisation
- This reaches a threshold and then it starts becoming more negative – repolarisation
17
Q
Voltage gated channels
A
- Along the axon, there are voltage gated channels for both sodium and potassium
- These open when a threshold voltage is reached
- As they open, ions passively flow along the chemical gradient until a threshold to close is reached
- Voltage channels close and become inactivated
- The will not open for some time – refractory period
18
Q
Steps of an action potential
A
- Start = RMP = -70mv
- Disturbance causes threshold voltage for Na+ voltage gated channels to open - -55mv
- Na+ voltage gated channels open
- Na+ rushes in – rapid depolarisation till +30mv
- Na+ channels close, K+ channels fully open
- K+ rushes out – repolarisation
- Overshoot – K+ continues to rush out beyond RMP since they close very slowly – hyperpolarisation –85mv
- K+ channels close
- Na+/K+ pump restores RMP and returns ions to their original positions
19
Q
Refractory periods
A
- Why does an action potential proceed only one way?
- The answer lies in the refractory period
20
Q
action potential In the case of myelinated axons
A
- The action potential is generated only at the nodes of Ranvier
- Saltatory conduction
21
Q
Synapses
A
- Nerve impulses travel in one direction
- The impulse crosses the synapse from the axon terminal of the first neuron to the dendrites of the next neuron
- In between neurons, a neurotransmitter carries the message across the synapse
22
Q
Divisions of the
nervous system
A
23
Q
The central nervous system
A
- The brain
- Fills the cranium
- Stops developing in the 15th year of life
- Main mass exercising control over the body
- Three section
- Cerebrum
- Cerebellum
- Brain stem
24
Q
The cerebrum - structure
A
- The largest part of the brain
- Divided into two cerebral hemispheres – left & right
- The outer layer is made of folds of grey matter
- Folds increase surface area
- There is white matter inside the grey matter
- White matter is composed of fibres which connect different parts
of the brain together
25
Q
The cerebrum - functions
A
- Controlling voluntary movement
- Interpreting and perceiving
conscious sensations like pain, heat and cold - Controlling mental activity eg memory, intelligence and reasoning
26
Q
The cerebellum -structure
A
- Also known as the small brain
- Positioned in the posterior cranial fossa behind the pons Varolii, below the cerebrum and over the medulla oblongata
- Consists of two hemispheres, grey matter on the surface, white matter underneath
52
Q
Function organisation of the PNS
A
56
Q
Sympathetic - functions
A
58
Q
Parasympathetic - functions
A
59
Q
Sympathetic/Parasympathetic graph
A
