Chapter 12: Coordination and Response in Humans

12.1 Coordination and Response

• Sensitivity is the ability to detect and respond to a stimulus; stimuli may be external (light, sound, smell, taste, temperature, pressure, touch) or internal (blood osmotic pressure, body temperature, blood sugar). (p.216)
• Pathway: stimulus → receptor → sensory neurone → integration centre (brain) → motor neurone → effector → response. (p.216)
• Baroreceptors in the aortic arch and carotid artery send impulses to the cardiovascular control centre in the medulla oblongata. (p.217)
• Coordination is done by the nervous and endocrine systems. (p.217)
• Receptors: photoreceptor (light), thermoreceptor (temperature), chemoreceptor (chemicals), baroreceptor (pressure), mechanoreceptor (touch and pressure), nociceptor (pain). (p.218)
• Responding to stimuli is necessary for survival and adapting to environmental change. (p.219)

12.2 Nervous System

• Central nervous system: brain and spinal cord. Peripheral: 12 pairs of cranial nerves and 31 pairs of spinal nerves. (p.220)
• Cerebrum: largest brain part; controls emotions, hearing, sight, personality, controlled actions, learning and memory. (p.221)
• Cerebellum: maintains body balance and muscle coordination. (p.221)
• Medulla oblongata: controls involuntary actions (heartbeat, breathing, digestion, blood pressure, coughing, swallowing). (p.221)
• Hypothalamus: homeostasis, regulates temperature, water balance, blood pressure, hunger and thirst; links to endocrine system via pituitary. (p.221)
• Pituitary gland: main endocrine gland controlling other glands. (p.221)
• Spinal cord: processes some sensory information, controls reflex actions, connects brain to the peripheral nervous system. (p.222)
• Dorsal root carries sensory neurone axons; ventral root carries motor neurone axons; grey matter has cell bodies; white matter has myelinated axons. (p.222)
• Somatic nervous system controls voluntary actions; autonomic controls involuntary actions. (p.222)

12.3 Neurones and Synapse

• Neurone parts: cell body, dendrites, axon, myelin sheath, node of Ranvier, synaptic knob. (p.223)
• Myelin sheath insulates and protects the axon; nodes of Ranvier let impulses jump and speed transmission. (p.223)
• Sensory neurones carry impulses from receptors to the CNS; relay neurones connect sensory and motor neurones; motor neurones carry impulses to effectors. (p.224)
• A synapse is the narrow gap between the synaptic knob and the next neurone's dendrite; it makes impulses travel in one direction. (p.224)
• Synaptic vesicles release neurotransmitters (acetylcholine, noradrenaline, serotonin, dopamine) that diffuse across and bind receptor proteins on the next neurone. (p.225)
• Synaptic knobs have many mitochondria to supply energy. (p.225)

12.4 Voluntary and Involuntary Actions

• Voluntary actions: conscious, controlled by cerebral cortex, use skeletal muscles and somatic nervous system. (p.226)
• Involuntary actions: automatic, autonomic nervous system, medulla oblongata and hypothalamus, smooth muscle and glands. (p.226)
• Reflex action is a fast response to a stimulus without control by the brain; the pathway is the reflex arc. (p.227)
• Three-neurone reflex arc: receptor, sensory neurone, relay neurone in spinal cord, motor neurone, effector. (p.228)
• Reflex actions give spontaneous responses and free the brain for higher thinking. (p.228)
• Knee jerk reflex uses two neurones (sensory and motor) and the quadriceps muscle. (p.229)

12.5 Health Issues Related to the Nervous System

• Parkinson's disease: tremors and difficulty with posture and balance. Alzheimer's disease: confusion and loss of reasoning and self-care. (p.230)
• ADHD, ALS (motor neurone death), autism, multiple sclerosis (myelin sheath attacked), epilepsy, cerebral palsy. (p.230)
• Stimulant drugs increase CNS activity; sedatives delay impulse transmission; hallucinogens cause hallucination; narcotics delay brain function; alcohol impairs coordination and thinking. (p.232)

12.6 The Endocrine System

• Endocrine glands are ductless and secrete hormones directly into blood; hormones affect specific target cells. (p.233)
• Hypothalamus secretes GnRH, stimulating pituitary FSH and LH. (p.234)
• Anterior pituitary: LH (ovulation, testosterone), GH (growth), ACTH (adrenal cortex), TSH (thyroxine), FSH (follicles, spermatogenesis). (p.234)
• Posterior pituitary: ADH (water reabsorption in kidney), oxytocin (uterine contraction, milk production). (p.234)
• Thyroxine raises metabolism; insulin lowers blood glucose; glucagon raises it; aldosterone increases salt reabsorption; adrenaline increases heart rate, respiration and blood sugar. (p.235)
• Oestrogen and progesterone (ovary), testosterone (testis) control sexual characteristics and reproduction. (p.235)
• Fight or flight: hypothalamus stimulates adrenal medulla to secrete adrenaline, raising heart rate, breathing, blood pressure and blood glucose. (p.236)
• Nervous system: electrical impulses, quick, short-lived. Endocrine: hormones through blood, slower, prolonged. (p.237)

12.7 Health Issues Related to the Endocrine System

• Diabetes mellitus: insufficient insulin gives high blood glucose; excess insulin causes hypoglycaemia. (p.238)
• Diabetes insipidus: no ADH from the posterior pituitary gives large urine volume and dehydration. (p.238)
• Hypothyroidism: too little thyroxine; hyperthyroidism: too much. (p.238)
• Gigantism: excess growth hormone in childhood; dwarfism: low growth hormone. (p.239)