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Integrated Systems Anatomy and Physiology (HUMB1001) Control of Body Systems Lecture Notes PART ONE - 2 Main control systems - Nervous system - For rapid response via action potentials and neurotransmitters - Controlled consciously (with cerebrum) or subconsciously (via somatic or autonomic reflexes) - Endocrine system - For slower prolonged response - Via feedback loops - Conscious control - For sensory information, impulse goes: receptor - sensory neuron - spinal cord - brainstem cerebral cortex - area concerning conscious awareness of stimuli - For motor information, impulse goes: area of brain concerning conscious desire to move brainstem - spinal cord via motor tracts - motor neuron - effector organ (muscle) - Requires central nervous system - Nerve impulse travels faster - Many more synapses - Decision needs to be made by conscious brain before a response occurs - More synapses slow the reaction time - Reflexes - Involuntary response to stimulus - Rapid, predictable and unlearnt - Cannot be improved by repetition - Reflex arc has five basic components: receptor, sensory neuron, interneuron, motor neuron and effector - Bypass the conscious part of the brain and can therefore occur without higher brain centre involvement - Minimal synapses - Functionally classified as either - Somatic - Deal with skeletal muscle - Remove the body from painful stimuli, keep balance and posture, and involves either the brain or spinal cord as the integration centre - Autonomic (visceral) - Involve the control of smooth and cardiac muscle, as well as body viscera - Used for maintaining bodily functions like homeostasis, movement of food through the digestive system, and the defecation and micturition (urination) reflex - Works on the same principles as other reflexes PART TWO - Brainstem - Primitive part of the brain - Mainly deals with integration centres - All information coming from or going to the spinal cord must travel through this region - Composed of: - Medulla oblongata - Most inferior part of brainstem, continuation to spinal cord - Lots of white matter tracts (both ascending and descending) - Many nuclei for integration of important reflexes (cardiac centre, gasometer centre, respiratory centre, hiccuping, coughing, sneezing, swallowing and vomiting) - Pons - Bridge between medulla/midbrain/cerebellum - Nuclei include sleep centre initiating REM sleep and respiratory centre (works in conjunction wiht the medullary rhythmicity centre) - Midbrain - Between pons and diencephalon - Has important nuclei for stabilising somatic movement - Reflex area includes - Visual - coordinates head and eye movement, tracking moving objects - Auditory - startle reflex - Diencephalon - Three parts make up the walls of the third ventricle - Hypothalamus - Inverted triangle shape - Controls many homeostatic mechanisms (body temp, sleep, food intake, water balance, thirst) - Connected to the pituitary gland - Anatomically through infundibulum - Functionally through blood vessels and nervous tracts - Thalamus - Sensory relay station - Epithalamus - Regulation of emotions and circadian rhythms - Pituitary gland - Small, pea sized gland - Divided into two parts: - Anterior - Made from glandular tissue, grows upwards from roof of mouth during embryonic stage - Large portion of the pituitary (70-80%) - Secretes hormones in response to releasing/inhibiting hormones from the hypothalamus - Releasing/inhibiting hormones travel to the anterior via a capillary network called the hypothalamohypophysial portal system - These stimulate or inhibit cells in the anterior to secrete their hormones into the blood - Hormones: (Letter - Hormone Name - Target tissue) - M - Melanocyte stimulating hormone - skin cells (melanocytes) - i - ignore - F - Follicle stimulating hormone - ovaries and testis - L - Luteinising hormone - ovaries and testis - A - Adrenocorticotropic hormone - adrenal cortex - T - Thyroid stimulating hormone - thyroid gland - P - Prolactin - ovaries and mammary glands - i - ignore - G - Growth hormone - most body tissues - Posterior - Made from nervous tissue - Smaller portion of the pituitary (20-30%) - Secretes only two hormones through neural secretion, however hormones are made in the cell bodies located in the hypothalamus and are transported down the middle of the axons to be released from the posterior - Hypothalamohypophysial tract goes down infundibulum to posterior - Hormones: - ADH - stimulates kidneys to retain water - Oxytocin - influence on smooth muscle of the uterus and mammary glands
