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Understanding the Brain and Nervous System

Explore the complex brain regions, from the cerebrum to the cerebellum, and understand neural organization and reflex actions. Learn how the body regulates temperature and the skin responds to maintain homeostasis.

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Understanding the Brain and Nervous System

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  1. Brain & Nervous System Chapter 15

  2. Brain • several main regions • - Cerebrum • - responsible for thought, reasoning, imagination etc. • - cerebellum • - controls balance & co-ordination • - medulla • - controls breathing & heart rate • - hypothalamus • - regulates water balance & body temperature • - pituitary gland • - releases many hormones (e.g. ADH)

  3. Cerebrum • Made of 2 cerebral hemispheres • Each split into different regions • E.g. sensory & motor strips • Sensory areas receive impulses from sense receptors • The more receptors the body part has, the bigger the sensory area it has • The impulses are interpreted and a response passed to the motor areas • The more mobile the body part, the larger the motor area it has • Both illustrated by a homunculus

  4. Organisation of the nervous system • Brain, spinal cord, and nerves = Central Nervous System (CNS) • Nerve cells are called neurones • Neurones consist of a cell body attached to nerve fibres • A sensory fibre takes impulses towards the CNS • A relay neurone passes the signal along the CNS • An axonfibre (motor neurone) that takes the response away • The synapse is the space between the end of one neurone and the beginning of another

  5. Reflex Action • Reflex is a rapid, involuntary response • e.g. hand contacting a hot surface • 1) Pain receptors in the skin detect heat • 2) Impulse sent along sensory neurone • 3) Impulse crosses synapse to relay neurone & is passed along • 4) Impulse crosses synapse to motor neurone • 5) Motor neurone takes response signal to the axon endings • 6) Signal is passed to the arm muscles & arm lifts

  6. Regulating body temperature • Hypothalamus -the body’s temperature monitoring centre • Receives nerve impulses from thermoreceptors in the skin • - to keep body shell at around 33oC • Also contains central thermoreceptorswhich detect blood temp changes • - keeps core temp at 37oC • Hypothalamus responds by sending motor nerve impulses to effectors

  7. Role of the skin • Acts in response to impulses from the hypothalamus • ‘Too hot’ - Promotes heat loss: • 1) Increases sweating rate by converting water in sweat to water vapour • 2) Vasodilation (arterioles get bigger) • - more blood flows to the skin surface(more heat lost as radiation)

  8. Role of the skin (ctd.) • ‘Too cold’ - Corrects overcooling: • - Decreases rate of sweating • - Vasoconstriction (arterioles become narrower) • - Less blood flow to skin surface (less heat lost by radiation) • - Erector muscles contract, hairs raised • - layer of air is trapped next to the body

  9. Other Effectors • Skeletal muscles undergo brief, repeated contractions – SHIVERING • In the liver, metabolic reactions are increased • - both help increase heat production

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