B13: Coordination and response

Human nervous system:

• central nervous system (CNS): brain + spinal cord

• peripheral nervous system (PNS): all nerves

  • sensory: sense organs → CNS (eye,nose,.. → CNS)

  • relay: sensory → motor muscles

  • motor: CNS → effectors (result in a response)

  • have long fibre (axon), electrical impulses jump from one node to the next

  • cell body has extensions called dendrites

Allows to:

• Sense our surroundings and respond to them

• Coordinated and regulate body functions

Information sent as electrical impulses along neurones

Bundle of neurones: nerve

Reflex arc:

• Voluntary response: conscious decision, starts at the brain → takes longer

• involuntary response: does not involve the brain, not aware of it until after it happens → essential to basic survival (rapid)

• reflex response: automatic and rapid response to stimuli which helps minimize damage to the body with the responses of effectors

  • an impulse is still sent to the brain but the brain isnt involved in the response

• reflex pathway stimulus:

  • receptor → sensory neurons → relay neurone → motor neuron → effector → response

Sense organs: a group of receptors that respond to specific stimuli

Chemical substance produce by a gland and carried by blood which alter the response of specific organs

come from endocrine gland:

• endocrine gland has a good blood supply to transport hormones into the bloodstream as soon as possible

• hormones only affect cells with target receptors that the hormone can bind to

• liver regulates hormone levels in the body

Important hormones

Glucagon: produced from the pancreas when blood sugar levels falls

• stimulates liver and muscle cells to convert stored glycogen into glucose to be released into the blood

Adrenaline: the hormone secreted in flight or fight situations

• increases blood glucose concentration for increased respiration

• increases breathing and pulse rate → glucose. oxygen delivered to muscle cells >< CO2 is taken away faster

• Dilating pupils to allow as much light as possible to reach the retina so more information can be sent to the brain

maintenance of a constant internal environment

negative feedback: any change away from set point triggers a response to reverse that change back to set point

• set point: ideal/normal value for a particular condition. eg. body temp (37 degrees)

• sensors: detect changes in the internal environment

• control centre: receives information from sensors and compares it to set point (triggers a response if moved away)

• effector: carries out the response to bring condition back to set point

Structure of the skin:

Hypothalamus (in the brain): detects a temp change in the body

Vasodilation occurs when the body is too hot

1. arterioles widen, more flood flows through capillaries

2. transfers heat from the blood to skin → lost through radiation

3. sweat glands become more active to cool down the body

Vasoconstriction: occurs when the body is too cold

1. arterioles constrict, reducing blood flow to the surface → minimizes heat loss

2. hair erector muscles contract → traps a layer of air providing extra insulation

3. body shivers → causes friction to heat up the body

Arterioles: blood vessels that get smaller/bigger, changes the blood flow to the capillaries of the skin. Capillaries dont change in size