Please enable JavaScript.
Coggle requires JavaScript to display documents.
M81Q1 - Homeostasis 2 - Coggle Diagram
M81Q1 - Homeostasis 2
The Nervous
System
Nervous System
- allows organisms to take in information from the environment and respond by passing information around the body through a network of neural pathways
- nervous system takes information from receptors, interprets the correct response, and sends messages to effectors.
- nerve impulses along neurons (electricity travels between neurons to deliver information).
Neurons
- functional units of the nervous system, which carry signals throughout the body.
- B DAMS
- cell Body: main spherical part of neuron, contains nucleus
- Dendrites: branch off cell body, extensions that connect the neuron to other neurons, carry info towards cell body.
- Axon: long, thread-like projection, carry info away from cell body.
- Myelin sheath: coats axon to protect and insulate.
- Synaptic knobs: branches from the end of the axon.
Components of the Nervous System
- central nervous system (CNS):
- brain + spinal chord
- gathers information from all over the body and coordinates responses.
- peripheral nervous system (PNS):
- nerves and receptors outside of the CNS
- neurones that connect the CNS to the rest of the body
PNS
- somatic:
- voluntary, conscious portion of nervous system.
- made up of nerves that connect to skin, sensory organs, skeletal muscles.
- processes sensory information that arrives via external stimuli, and controls skeletal muscles which allows voluntary movement.
- autonomic:
- involuntary, unconscious portion of nervous system
- made up of nerves that connect to the cardiac muscle in the heart and the smooth muscle in the organs.
- controls heart rate, digestion, salivation, sweating, pupil diameter, etc.
Autonomic Modes Based on Stress Levels:
- parasympathetic:
- calm and relaxed
- nervous system realises you're not in danger and releases neurotransmitter called acetylcholine.
- heart slows to normal, digestive system continues to digest food.
- sympathetic:
- stressed
- nervous system realises you're in danger and releases adrenaline
- adrenaline tells heart to speed up in order to get blood pumping around body so that muscles have better access to oxygen
- digestion is stopped to focus energy towards survival
Types of Neurons
- sensory neuron: carry electrical impulses from receptors to CNS.
- long dendrites to receive sensory info from receptors.
- motor neurons: transmit electrical impulses from CBS to effectors (muscles, organs, glands).
- long axon to send sensory info to effector cells.
- interneurons: transmit electrical impulses between sensory and motor neurons.
- found exclusively in CNS.
- many, short dendrites to carry nerve impulses from sensory neurons to cell body. many, short axons to carry nerve impulses from the cell body to motor neurons.
The Endocrine
System
Endocrine System
- a group of glands which secrete hormones
- a hormone is a small chemical which causes a response in another region of the body. produced by glands.
- circulatory is the main system for hormone transport, but lymphatic is also used sometimes.
- hormones diffuse out of glands and into the blood, to be taken around the body by the circulatory system.
- each hormone will only bind to specific receptors for that hormone found on target cells (target tissues contain target cells)
Glands and
Hormones
Brain
- Hypothalamus
- controls many metabolic processes, including thermoregulation
- determines whether optimal conditions are being maintained.
- secretes thyrotropin releasing hormone (TRH) > triggers the release of thyroid stimulating hormone (TSH) > causes T3 and T4 to be released.
- produces antidiuretic hormone (ADH) which increased water absorption into the blood from the kidneys.
- Pituitary Gland
- controlled by the hormone secretions of the hypothalamus
- releases several hormones to regulate the secretion of hormones from other glands.
- posterior pituitary gland regulates ADH production.
- anterior pituitary gland regulates production of TSH, growth hormone, FSH.
- Pineal Gland
- secretes melatonin
- control circadian rhythms (24hr bio cycles for eating, sleeping, etc) and regulates reproductive hormones
Thyroid
- controlled by pituitary
- found around neck, alongside parathyroid gland.
- secretes T3 and T4 (involved in thermoregulation)
- parathyroid gland secretes parathyroid hormone, which triggers calcium release into the blood.
Thymus
- responsible for development of immune system
- secretes thymosin, which stimulates the development of T cells
Pancreas
- behind stomach
- controls blood glucose levels
- secretes glucagon and insulin
Adrenal
- help body respond to stress and control blood pressure
- secrete aldosterone (found in adrenal cortex), adrenaline and noradrenaline (found in adrenal medulla)
Gonad
- progesterone and estrogen produced by ovaries
- promote healthy development of female sex characteristics during puberty.
- encourage fertility
- testosterone produced by testes
- involved in masculine development
- 3 ways for glands to be stimulated and make and release hormones:
- neural stimuli: receiving nerve impulses
- hormonal stimuli: detecting change in the concentration of a hormone
- humoral stimuli: detecting change in the concentration of another substance in the blood.
- response = hormone binds to target cell
- cell's sensitivity to a hormone is linked to number of receptors found on the outside of the cell: lots = dramatic response, few = down-regulated response.
System Comparison
Nervous
- instantaneously sends electrical impulses
- localised to a specific cell or tissue
- temporary response
Endocrine
- slower communication of message to effector.
- hormones can have effects on tissues that are widely distributed around the body.
- a tissue just needs hormone receptors in order to be affected.
- systemic response (cells or tissues throughout the body)
- long-lasting response
- both share homeostatic processes like thermoregulation, osmoregulation and glucose homeostasis.