muscle vs ligament
muscle: contract, relax, allow movement
ligament: taut, slacken, connect bone to bone
photoreceptors
rods and cones
outermost layer to innermost
sclera, choroid, retina
blind spot and fovea no rods and cones
little to no part of retina at blind spot and fovea
forming an image on retina
- cornea and aqueous humour refract light rays on lens
- lens further refract and converge light rays on retina
- image formed is upside down, laterally inverted and smaller
focusing
adjust lens so clear images of objects are formed on retina
focusing on distant object (CRST)
- ciliary muscles relax
- suspensory ligament become taut
- lens become thinner, less convex
focusing on near objects (CCSS)
- ciliary muscles contract
- suspensory ligament slacken
- lens become thicker, more convex
binocular vision
usage of two eyes to perceive a 3d image of the surroundings
(PUPIL REFLEX) iris control amt of light entering eye in BRIGHT LIGHT (CCRR)
- Circular muscles contract
- Radial muscles relax
- Pupil constricts, less light enter eye
(PUPIL REFLEX) iris control amt of light entering eye in DIM LIGHT (RCCR)
- Radial muscles contract
- Circular muscles relax
- Pupil dilates, more light enter eye
central nervous system
brain and spinal cord
peripheral nervous system
cranial and spinal nerves, sense organs
relay neurone function
relay impulses from sensory neurones to motor neurones, contains many short nerve fibres
synapse
junction between two neurones
how do CNS and PNS work tgt
when there is a stimulus,
1. Receptors in sense organs are stimulated to produce nerve impulses
2. Nerve impulses transmitted to CNS
3. CNS send nerve impulses to effectors (either muscles or glands)
reflex action
an immediate response to a specific stimulus without conscious control
reflex arc (shortest pathway for nerve impulses to travel from receptor to effector in reflex action)
- receptor
- sensory neurone
- relay neurone (CNS)
- motor neurone
- effector
how does the body lose heat
- from skin surface through convection, conduction and radiation
- evaporation of sweat
- faeces and urine
- exhaled air
how is body temperature regulated
- hypothalamus does it
it receives info from thermoreceptors on skin surface (temp of external environment) and hypothalamus itself (temp of blood)
body temp increase
- thermoreceptors in skin/hypothalamus detect increase
- vasodilation of arterioles near the skin surface
- increased production of sweat
- decreased metabolic rate
- increased heat loss, reduced heat production
- body temp decrease till normal.
body temp decrease
- thermoreceptors in skin/hypothalamus detect decrease
- vasoconstriction of arterioles near the skin surface
- decreased production of sweat
- increased metabolic rate
- shivering occurs (only in extreme cases)
- decreased heat loss, increased heat production
- body temp increase till normal.
