Unit 1 Nervous System and Endocrine Sytem

• hypothalamus = oxytocin, adh

The hormones secreted form the hypothalamus (oxytocin and ADH) are specialized for the uterus, breast and the kidneys. Oxytocin stimulates the contraction of the uterus and also stimulates the mammary glands, resulting in breast milk. ADH causes the kidneys to remove water from urine that is forming

The hypothalamus secretes releasing factors which stimulates the secretion of a hormone, or inhibiting factors which slow down the secretion of a hormone. These factors travel through blood vessels to the anterior lobe of the pituitary gland

Steroids are lipid soluble and their mode of action follows the following four steps; 1. Hormone diffuses across the cell membrane (lipid soluble) • Hormone attaches to the receptor in the cytoplasm/ on the nucleus (hormone-receptor complex formed) • Hormone-receptor complex enters the nucleus • Hormone receptor complex activates genes/transcription of mRNA (complex binds to DNA)

Protein or amine hormones are water-soluble and follows the following four steps; • Hormone stays on the outside of the cell membrane (water soluble) • Hormone attaches to the receptor on the surface of the cell membrane (hormone-receptor complex forms) • Secondary messenger is activated which diffuses through the cytoplasm • Activates enzymes in the cytoplasm

Exocrine - secrete into a duct that carries the secretion to the body surface or to one of the body cavities I.E - sweat glands, mucous glands, salivary glands Endocrine - secrete hormones into the extracellular fluid that surround the cells that make up the gland I.E - hypothalamus, pituitary, thyroid, parathyroid, adrenals, pineal

Hypothalamus - brain Pineal - brain Pituitary - brain Thyroid - throat Parathyroid - throat Thymus - chest Adrenal - kidney pancreas - itself

Paracrine - relating to or denoting a hormone which has effect only in the vicinity of the gland secreting it. Hormones - a chemical that is secreted by the endocrine gland that affects the functioning of a cell or organ; often carried in the blood

Label the; nucleus, axon, dendrite, cell body, neurilemma, node of Ranvier, myelin sheath Function - functional units of the nervous system. Highly specialised cells which are perfectly designed for rapid communication of messages in the body

1) Polarisation - At a resting, potential the membrane is polarised-inside of the cell and has a net negative charge and the outside of the cell has a net positive charge. A Na/K pump allows these ions to move across the membrane: sodium into the cell and potassium out 2) Depolarization - the sudden increase in membrane potential - This occurs if the level of stimulation exceeds 15mV - Once they are open, more sodium ions move into the cell. this makes the intracellular fluid less negative, increasing the potential difference - If the stimulus is strong enough to increase the potential to -55mV then voltage-gated sodium channels open - This produces a movement of sodium ions into the cells - The size of the response is not related to the strength of the stimulus, this is also known as the all or none response 3) Repolarization - The sodium channels close, which stops the influx of sodium ions - At the same time, voltage-gated potassium channels open, increasing the flow of potassium ions out of the cell - This makes the inside of the membrane more negative than the outside and decreases the membrane potential - The membrane is repolarized - The potassium channels remain open longer than what is needed, this results in the membrane potential dropping lower than the resting membrane potential, and the membrane is hyperpolarised - This process is called hyperpolarization 4) Refractory Period - Once the sodium channels have opened they quickly become inactivated - Thus being unresponsive to stimulus - Therefore, for a brief period after being stimulated, the membrane will not undergo another action potential

• pituitary = fsh, lh, gh, tsh, acth, prl

• thyroid = Thyroxine and T3

• pancreas = Insulin and glucagon

• parathyroid = PTH

• adrenal = Adrenaline and corticosterioids

The hormones secreted from the pituitary (FSH, LH, GH, TSH, ACTH & PRL) are specialized for the testes, adrenal cortex, thyroid gland and mammary glands. The have many effects namely; LH - stimulates sperm production, growth of skin and muscles TSH - increases metabolic rate ACTH - promotes normal metabolism and stimulates the reabsorption of sodium ions in the kidney

thyroxine and T3 or Triiodothyronin - affects metabolic rate, directly impacting the liver and kidneys

PTH specialized for bones and kidneys and it increases the calcium levels in the blood

the pancreas secretes insulin and glucagon. Insulin regulates the body’s energy supply, whilst glucagon stimulates the breakdown of glycogen and fat

the adrenal gland secretes cortisol and adrenaline Cortisol promotes normal metabolism and adrenaline prepares the body for fight or flight responses

The maintenance of a relatively constant internal environment despite fluctuations in the external environment

Internal - core temperature - detected by thermoreceptors within the hypothalamus, detecting the temperature of the blood flowing through the brain External - changes in temp outside the body - skin thermoreceptors inform the brain of changes

Central Structure - brain and spinal chords - protected by bone, meninges and cerbrospinal fluid Function - receives and processes incoming messages and outgoing messages are initiated Peripheral Structure - cranial nerves and spinal nerves Function - takes messages from receptors to the CNS and from the CNS to muscles and glands

Afferent Structure - nerves and neurons Function - carry impulses into the CNS Efferent Structure - nerves and neurons - carry away from the CNS - divided into somatic and autonomic Function - carry impulses away from the CNS