The Nervous System/brain/thermoregulation

• The nervous system enables humans to react to their surroundings and to coordinate their behaviour.
• The nervous system uses electrical impulses to bring about fast, but short-lived, responses.
• The nervous system consists of the brain and spinal cord, which together form the central nervous system. The CNS is linked to sense organs by neurones, which form the peripheral nervous system.
• Neurones are specialised cells which carry electrical impulses
• dendrites. - receive incoming impulses from other neurones.
• axon. – a single nerve fibre that carries nerve impulses away from a cell body which is insulated by a fatty sheath. Normally long and thin, they are used to carry messages all round the body.
• fill in gaps

  A) nucleus

  B) dendrite

  C) nerve ending

  D) cytoplasm

  E) axon

  F) schwann cell

  
• Nerve impulses cannot cross the gap between neurons but chemicals can cross them instead. 
• The gap between two neurones is called the synapse.
• stimulus → receptor → coordinator → effector → response
• 1. An electrical nerve impulse travels along the axon of the first neuron (presynaptic neuron).
• 2. When the nerve impulse reaches the dendrites at the end of the axon, chemical messengers called neurotransmitters are released.
• 3. These chemicals diffuse across the synaptic cleft. The chemicals bind with receptor molecules on the membrane of the second neuron (postsynaptic neuron).
• 4. The receptor molecules on the second neuron can only bind to the specific neurotransmitters released from the first neuron.
• 5. The binding of the neurotransmitter to the receptors will stimulate the second neuron to transmit an electrical impulse along its axon. The signal therefore has been carried from one neuron to the next.
• Reflex actions are rapid, automatic responses of the nervous system which do not involve the involvement of the brain
• For a reflex action, signals pass directly from a sensory neurone, via a relay neurone, to a motor neurone . This nervous pathway is known as a reflex arc.
• A reflex arc is very important because it allows us to avoid danger or harm, as well as allowing us to coordinate everyday bodily functions
• receptors detect stimuli.
• stimuli are any changes in the environment
• coordination centers receive and process information from receptors
• effectors bring about responses that restore optimum levels.
• state an investigation that could be carried out to determine the effect of a factor on human reaction times.

  ruler drop test
• label the diagram

  A) cerebral cortex

  B) cerebellum

  C) spinal cord

  D) medulla

  E) pituitary gland

  F) hypothalamas

  
• the cerebrum controls intelligence, personality, conscious thought and high-level functions, such as language and verbal memory.
• The cerebellum controls balance, coordination of movement and muscular activity.
• the medulla  controls unconscious activities such as heart rate and breathing rate
• the hypothalamus is the regulating centre for temperature and water balance within the body.
• Different ways to study the brain are :

  • studying brain damage
  • MRI scans
  • electrical stimulation
• due to the complexity and delicacy of the brain, investigating and treating brain disorders, surgery is undergone more damage or side-effects may be created, which could affect the patients' quality of life.
• Body temperature is monitored and controlled by the thermoregulatory centre in the brain
• The thermoregulatory centre contains receptors sensitive to the temperature of the blood. The skin contains temperature receptors and sends nervous impulses to the thermoregulatory centre.
• When we get too hot sweat glands in the skin release more sweat. The sweat evaporates, transferring heat energy from the skin to the environment.
• What is vasolidation?

  when it is too hot, blood vessels to the skin capillaries become wider - they dilate - allowing more blood to flow through the skin, and more heat to be lost to the environment. 
• When we get too cold: Skeletal muscles contract rapidly and we shiver. These contractions need energy from respiration, and some of this is released as heat
• What is vasoconstriction?

  Blood vessels, which lead to the skin capillaries, become narrower - they constrict – which allows less blood to flow through the skin and conserve the core body temperature. 
• If we are too cold nerve impulses are sent to the hair erector muscles which contract. This raises the skin hairs and traps a layer of insulating air next to the skin.
• The control of body temperature is an example of a negative feedback mechanism.
• gapsule

  A) constriction

  B) dilation

  C) narrow

  D) wide

  E) decrease

  F) increase

  
• fillip

  A) heat

  B) dilates

  C) constricted

  D) hypothalamas