Describe the different components of the peripheral nervous system and how electrical impulses are transmitted. Flashcards
1
Q
Give an overview of the nervous system?
A
2
Q
Describe the features of cell body (2), dendrites (1), axon (2), nodes of ranvier (2)?
A
- Cell body:
- Contains nucleus
- Proteins produced here
- Dendrites:
- Towards cells body (receives and processes)
- Axon:
- Away from cell body
- Arises at axon hillock
- Nodes of Ranvier:
- Unmyleinated areas between myelinated areas
- APs to ‘jump’ node to node = saltatory conduction
3
Q
What is a motor unit?
A
- 1 axon and all the muscle fibres it supplies
4
Q
What is the PNS? and what does does it consist of
A
- Connection - CNS and body
- Peripheral nerves (cranial and spinal)
- Motor and sensory neurones
5
Q
The PNS and two components:
A
- Sensory (afferent) division
- Sensory neurones
- Receptors to CNS
- Motor (efferent) division
- Motor neurones
- CNS to effectors
6
Q
The motor division has two components:
A
- Somatic Nervous System:
* Controls vascular movements - Autonomic Nervous System:
* Controls involuntary responses e.g. heart rate
7
Q
The autonomic nervous system has two components which work…. and why?
A
- Antagonistically
- Maintenance of homeostasis
8
Q
The autonomic nervous system has two components
A
- Sympathetic
- Mobilises body systems
- Flight or fight
- Parasympathetic
- Conserves energy
- Rest and digest
- Controls simple involuntary reflexes
9
Q
Give the 4 steps involved in the flight or fight response:
A
- Stressor –> amygdala activated –> impulses to hypothalamus
- ANS switches from PNS to SNS –> impulses to adrenal medulla = adrenaline and noraadrenlaine
- Hormone = physioloigcal changes
- Threat passsed - SNS to PNS
10
Q
Give 6 examples of complementary phsyiological chances during a sympathetic and parasympathetic state:
A
11
Q
- What is the resting potential
- What is the main reason the resting potential occurs? (3)
- How is the membrane potential maintained?
A
- -70 mV
- Ions are unevenly distributed
- More permemable to K+ than Na+
- More negative inside than out = more +ve ions flow out than in
- Na+/K+ pump (3 Na+ out for every 2K+ in)
12
Q
Define the term action potential?
A
- A transient depolarisation triggered by a depolarisation beyond a threshold
13
Q
D
A
- Resting potential (-70 mV)
- Electrical stimulus = voltage gated Na+ channels open
- Threshold (-55 mV) reached = more voltage gated Na+ channels open
- At +40 mV = voltage gated Na+ channels close and voltage gated K+ channels open.
- Repolarisation - K+ move down their electrochemical gradient
- Hyperpolrisation - Membrane potential overshoots
- Relative refractory period
- Resting membrane potential = Na+/K+ pump
14
Q
Explain the propagation of action potential in an unmyelianted axon?
A
- AP is propagated along the entire length of the axon
- More voltage-gated Na+ channels are opened as depolarisation spreads.
15
Q
Speed of conduction depends on 3 main factors:
A
- Myelin sheath:
- Electrical insulator
- AP jump node to node via saltatory conduction
- Diameter of Axon:
- Larger diamter = faster speed of conductance = less leakage of ions
- Temperature:
- Higher temp = faster speed of conductance = enzymes work faster
