Chapter 13 (Neuronal Communication) Flashcards
(50 cards)
How does the Pacinian corpuscle convert mechanical pressure into a nervous impulse
1) In the resting state, stretch mediated sodium ion channels are closed, so the Pacinian corpuscle has a resting potential
2) Pressure= surrounding membrane stretches
3) Therefore, sodium ion channels widen and diffusion occurs
4) An influx of positive ions depolarises the membrane = generator potential
5) Generator potential creates an action potential (nerve impulse) and passes along the sensory neurone
How is a resting potential established?
1) Sodium-potassium pump moves 3 Na+ ions out and 2 K+ ions into the axon
2) Therefore, there mare more Na+ ions outside the membrane and more K+ ions inside, so both diffuse down their respective electrochemical gradients
3) However, most gated sodium ion channels are closed but potassium ion channels are open, meaning that only K+ ions can diffuse, resulting in a positive outside and negative inside (resting potential of -70mv)
What is the value of resting potential across a membrane?
-70mv
What are the stages of myosin binding to actin in the sliding filament model?
1) Tropomyosin blocks binding site on actin molecule
2) Ca2+ ions released from endoplasmic reticulum causes tropomyosin to move away from the binding sites
3) Myosin head (with ADP molecule) attaches to the binding site on actin filament
4) Myosin head changes angle, moving actin filament and ADP is released
5) ATP molecule attaches to myosin head, causing the head to detach from actin
6) Hydrolysis of ATP to ADP provides energy for myosin head to go back to its original position
7) Myosin head attaches to actin binding site further along and the cycle is repeated
What are the cells called that make up the myelin sheath?
Schwann cells
Where is the cell body on a sensory neurone?
Cell body is found on an offshoot from the axon/dendron
Where is the cell body on a relay neurone?
Cell body is near the start of the neurone, connected to the dendrites by a short dendron
Where is the cell body on a motor neurone?
Cell body is at the start of the neurone, where all the dendrites meet
When is ADP released from myosin?
When the myosin head changes angle while bounded to the actin
What is the Cerebrum and what does it do?
Made up of the 4 lobes, controls voluntary actions
What is the cerebellum and what does it do?
Controls unconscious functions, but does not initiate them
What is the Medulla oblongata and what does it do?
Part below the pituitary gland, used in autonomic control (e.g. breathing and heart rate)
What does the hypothalamus do?
• Regulatory centre for temperature and water balance
• Main control for the autonomic nervous system
What does the pituitary gland do?
• Anterior pituitary- Produces six hormones, such as FSH
• Posterior pituitary- store and release hormones
What is homeostasis?
When the internal environment is kept within a narrow range
What is cell signalling?
One cell releases a chemical which affects another cell
What is the electrical impulse pathway?
(Stimulus)
1) Receptor
2) Sensory neurone
3) Relay neurone
4) Motor neurone
5) Effector cell
(Response)
What is a node of Ranvier?
The gap between adjacent Schwann cells
What are the 4 types of sensory receptors, and where can they be found?
Mechanoreceptor- skin (Pacinian corpuscle)
Chemoreceptor- nose (olfactory receptor)
Photoreceptor- eye (cone cells)
Thermoreceptor- tongue (end-bulbs of Krause)
How do action potentials propagate?
1) There are more positively charged ions outside of the cell, so the membrane is polarised
2) Stimulus causes an action potential, depolarising the membrane
3) Influx of Na+ ions causes channels to open a little further along the axon, causing more depolarisation. At the start of the axon, V-G NA+ channels close and K+ ions leave down an electrochemical gradient
4) The start of the membrane becomes repolarised while the action potential is propagated along the axon
5) The membrane begins to return to its resting potential to receive another impulse
What is the time called when the axon cannot be excited again?
The refractory period
Why is the refractory period important?
Ensures impulses only travel forwards and are distinct from each other
What is saltatory conduction?
When the action potential jumps from one node of Ranvier to another. This is because the membrane only has to be depolarised at the nodes. More energy efficient
What factors affect the speed of action potential transmission?
• Myelination
• Axon diameter (Bigger=faster, as there is less resistance)
• Temperature