B10: Human Nervous system

What is the function of the nervous system?

What is the function of the nervous system?

it enables organisms to react to their surroundings and coordinates behaviour

What are the two parts of the central nervous system?

brain and spinal cord

Why are reflex actions described as rapid and automatic?

impulse bypasses the concious areas of brain so time between timulus and reflex action is as short as possible

Why are reflex actions important?

for survival to prevent damage to the body and also help basic body functions (Eg breathing & moving food through digestive system)

Give the pathway of a nervous response.

stimulus ➞ receptor ➞ coordinator ➞ effector ➞ response

What is homeotasis?

Regulation of the internal conditions of cells to maintain optimum conditions for functioning

Why is it important to maintain optimum conditions for cellular enzymes?

They control functions of the cells such as body temperature, water content of the body and the blood glucose concentration

Name two automatic control systems:

Nervous responses in nervous system and chemical responses in hormone system

What do receptors do?

Detect the stimulus in the internal/external environment part of nervous or hormonal control systems.

What do effectors do?

muscles or glands that bring about responses to the stimulus that has been received which restore conditions in body to optimum levels

What does the coordination centre do?

Receives and processes the information from receptors then sends signals to cordinate response of body to effectors

Explain the pathway of the control system when there is a change in body temperature:

Skin receptors detect the stimuli and send nervous impulses to brain where it is then received and organised to send signals to skeletal muscles to contract (shiver) when it's cold or to sweat glands to release more sweat when it's too hot

Explain the pathway of the control system when water content in the body changes:

There is a change of water concentration either inside or outside cells so burst or shrivel which causes recepters that monitor concentration of water in blood to send signals to the brain where it sends nervous reponses to the kidneys to remove excess water or control the amount of water lost

Explain the pathway of the control system when there is a change in blood glucose concentration:

Receptors detect change in blood so send nervous signals to the coordination centre where it will send impulses to the pancreas to secrete insulin to lower blood levels or to the liver / muscle cells where excess glucose is converted into glycogen for storage

Name examples of stimulus:

Light, sound, pressure, pain, change in temp, chemical (taste), touch, smell

Explain a nervous response to a stimulus:

Once a receptor detects a stimulus, the information is sent as an electrical impulse that passes along the sensory neurone to the CNS where it coordinates a response and sends impulses along the motor neurones to effectors

What are neurones made of?

Bundles of thousands of nerves

How do muscles effectors respond to electrical impulses?

By contracting

How do glands effectors respond to electrical impulses?

By secreting chemicals

REQUIRED PRACTICAL: How could a student measure reaction times?

Use ruler drop test or digital sensors to measure how quickly the student reacts to visual stimulus

What are reaction times?

how quickly nerve impulses travel in the body

Factors that affect reaction time:

Tiredness, distractions, caffeine, alcohol

What are reflexes?

Automatic responses to certain stimuli

Describe the reflex arc pathway:

stimulus --> receptor --> sensory neurone --> relay neurone --> motor neurone --> effector --> response

What is the difference between a nervous reponse and a reflex response?

Within the reflex arc, electrical impulses are received and organised at the relay neurone instead of the CNS

What do the relay neurones do?

connect the sensory neurone to the motor neurone

What are synapses?

junctions between neurones that form physical gaps which allow electrical impulses to cross between neurones

Explain how electrical impulses travel across synapses:

When an impulse arrives at a synapse it will release a chemical into the gap between neurones where it will diffuse (across synapse) to the surface of the next neurone to set off a new electrical impulse

What are dendrites in nerve cells?

Branched endings that make connections with other neurones or effectors

What is the purpose of the myelin sheath surrounding nerve cells?

Insulates the axon which increases speed of electrical impulses

What do axon terminals attach to?

Effectors

What is the chemical substance that crosses the synapse?

Neurotransmitter