Topic 14 Flashcards
2 parts of nervous system
- central nervous system (brain and spianl cord)
- peripheral nervous system (neurones outside CNS)
Synapses
- a junction between 2 neurones
- consists of 2 neurones separated by a synaptic gap
- the neurone BEFORE the gap hold vesicles filled with neurotransmitters
- the endnof the neurone AFTER the gap has neurotransmitter receptor proteins
- nervous impluse passed across synapse: the nerve impluse reachesnthe end of the neuron before the synaptic gap and triggers the release of neurotransmitter molecules from versicles across synaptic gap; they diffuse across the synaptic gap and then bind to the neurotransmitter receptor proteins in the membrane of the next neurone; stimulates and electricsl impulse in next neurone.
Reflex actions
Rapid, automatic responses to stimuli that don’t involve the concious part of the brain - body reacts without thinking
Central nervous system
Stimulus (detected by receptors) - impluses go through sensory neurone - impulse reaches synapse between sensory neurone and relay neurone - sent along relay neurone - motor neurone - sent to effector (muscle/gland)
Sense organ
Group of receptor cells that respond to a specific type of stimulus
Iris
Contains muscles that control the diameter of the pupil
Cornea
Transparent outer layer, refracts light into eye
Blind spot
No light receptors
Lens
Focuses light on the retina
Pupil
Hole in the middle of the eye
Fovea
Specifc area containing cones
Optic nerve
Carries impulses from receptors to brain
Retina
Contains rods and cones
Rods
Found in peripheral parts of retina, sensitive to light (work well in dim light), gives information in black and white
Bright light reflex
Pupil shrinks, circular muscles contract, radial muscles relax
Dim light reflex
Pupil widens, radial muscles contract, circular muscles relax
Near objects
Cilary muscles contract, suspensory ligaments slacken. Lens becomes fat increasing how much refracts.
Distant objects
Cilary muscles relax, suspensory ligaments tighten. Lens goes thin, refracts by a smaller amount
Hormones
Chemicals produced by glands amd carried by the blood, which change the activity of a specific target organ or organs.
Ovaries - hormone
Produces oestrogen (only females)
Adrenal glands
Produce adrenaline
Testes
Produce testosterone (males only)
Pancreas
Produces insulin and glucagon
Insulin
Decreases blood sugar level when it gets too high
Oestrogen
Main female sex hormone. Involed in menstrual cycle and promotes development of secondary sexual characteristics
Testosterone
Main male sex hormone.controls sperm production and development of secondary sexual characteristics
Adrenaline
- prepares you for ‘fight or flight’
- when brain detects a dangerous or stressful situation it sends nerve impulses to adrenal gland to secrete adrenaline.
- causes increase in breathing rate and heart rate and causes pupils to widen.
- increase in heart and breathing rate imcrease metabolic activity - more blood flow to muscles so cells recieve more oxygem and glucose for respuration
- adrenalime also causes liver to break down its glycogen ans release glucose
Nerve impulses
Fast message, act for a short time
Hormone
Slower message, acts for longer
Homeostasis
The maintenance of a constant internal environment e.g body temperature 37 degrees
- conditions are kept steady by negative feedback system
Mechanisms to reduce body temperature
Hairs lie flat, sweating, vasodilation
Vasodilation
Whem it is hot arterioles near the surface of the skin dialate. more blood flows through the surface of the skin more heat lost temp lowered
Mechanisms to increase body temperature
Hairs stand up, much less sweat, shivering , vasoconstriction
Vasoconstriction
When its cold arterioles near the surface constrict so less blood flows through thr capillaries in the suface layers of the skin. This reduces heat loss
Controlling Blood Glucose Concentration
- excess glucose can be stored as glycogen in the liver and in muscles
- changes in glucose levels are controlled by the pancrea using insulin and glucagon
- when blood glucose concentration is too HIGH - INSULIN is secreted
. when insulin makes liver turn glucose into glycogen
. glucose moves from blood into liver and muscles cells - when blood glucose concentration is too LOW - GLUCAGON is secreted by pancreas
. glucose released into blood by liver
. glucagon makes liver turn glycogen into glucose
Type 1 diabetes
- caused by lack of insulin produced by pancreas
- treated with insulin therapy
- injections usually done at meal time
- not eatong too many simple carbs (sugars), taking regular exercise (removes excess glucose)
