The Nervous System Flashcards
Definition of homeostasis?
Maintaining a stable internal environment within the body
Examples of how homeostasis helps the body?
Negative feedback loops, water regulation, temperature control
Which parts of the body are part of the central nervous system?
Brain, spinal cord and relay neurones
What makes up the Peripheral Nervous System?
The Somatic and Autonomic Nervous Systems
The difference between somatic and autonomic?
Somatic is voluntary (muscles and skin) and the autonomic is involuntary (organs)
What is the autonomic nervous system made of?
The sympathetic and parasympathetic nervous systems
The Sympathetic Nervous System?
Activated in times of stress, your ‘fight or flight’ instincts
The Parasympathetic Nervous System?
Controls your body in times of rest
The neurotransmitters used in sympathetic and parasympathetic?
Sympathetic = Noradrenaline (Na)
Parasympathetic = Acetylcholine (ACh)
Peristalsis?
Involuntary muscle movement involved in digestion in small intestine
Name the parts of a motor neuron?
Cell body, Dendrites, Axon, Axon terminals, Nodes of Ranvier, Schwann cells and myelin sheath
What is a node of Ranvier?
The small gap between the Schwann cells
Where does depolarization occur in the neuron?
The Nodes of Ranvier
The name for when a neuron has Schwann cells and a myelin sheath?
Myelinated axons
The name for when the electrical impulse skips a node?
Saltatory conduction
What physical difference is there between motor and relay neurons?
Relay neurons have a shorter axon and a larger cell body
What is the Pacinian corpuscle?
A specific sensory receptor that detects mechanical pressure
Definition of a transducer?
Something that converts a stimulus into action potential / nerve impulse
Differences that a sensory neuron has?
Has a dendron at the top instead of an axon near the dendrites, cell body is down the side and smaller as well
Reflex arc, what is it?
A genetic survival mechanism
Where is the Pacinian corpuscle normally?
In fingers, joints and feet
Type of neurons found in the spinal cord?
Sensory and motor neurons
How does the Pacinian corpuscle help the neuron?
Helps convert mechanical pressure into a nervous impulse
The 4 main types of sensory receptor?
Mechanoreceptor (pressure and movement), chemoreceptor (chemicals), thermoreceptor, photoreceptor (light)
What are dendrons responsible for?
Passing the electrical impulse towards the cell body
What is a myelinated axon?
A plasma membrane made up of many phospholipid bilayers, transmits impulses faster
Features of sensory neurons?
Specific to stimulus, act as transducers (convert stimulus into impulse)
Normally what is an effector?
A muscle or gland
Structure of the Pacinian corpuscle?
End of sensory neuron found within center, surrounded by layers of connective tissue, each layer separated by gel
What happens when the sodium ion channels change shape in the membrane?
Their permeability will change, when too narrow for sodium the neuron has resting potential, when stretched it then has action potential
Potential difference across membrane when at resting potential?
-70mV
Potential difference across membrane when at action potential?
Around 40mV
Charge inside axon during resting potential?
Axon = Negative
Tissue fluid = Positive
How do the charges change once wave of depolarization has occurred?
The axon becomes positively charged and the tissue fluid is negatively charged now
How do K+ ions leak out the axon?
Facilitated diffusion
When pressure is applied to the Pacinian corpuscle what happens?
It will change shape and stretch the sodium ion channels allowing more sodium ions to pass through
Once sodium ion channels have been stretched what happens now the sodium concentration has increased?
The influx of sodium ions changes the potential of the membrane, it becomes depolarized
The ratio for Na+ to K+ pumped in and out?
For every 3 Na+ ion there is 2 K+ ions
During resting potential where is there a higher concentration of sodium ions?
Outside in the tissue fluid
What actively pumps the Na+ and K+ ions in and out of the neuron?
ATPase by active transport
When can a stimulus set up an action potential?
Only when its above a threshold level
What happens when stimulus is under the threshold?
Gated channels remain closed, no depolarization which means no action potential
What is the net result of ions in resting potential?
More sodium ions outside axon than K+ ions inside
Which gates are open during depolarization?
Sodium gates are open allowing them to move into the axon and change the charge to positive
Which gates are open during repolarization?
Potassium gates open and move out through facilitated diffusion down a conc gradient
What is the refractory period?
After repolarization, Na+ and K+ ions remain closed so membrane can’t be depolarized, no impulse can pass
How long is the refractory period?
0.5ms
What is the importance of the refractory period?
Makes each action potential distinct, keeps it travelling one way
How many mV is the threshold for an action potential?
-55mV
