Nervous System Flashcards
why is the nervous system important
allows our bodies to respond to the environment
what are the 2 nervous system types
- the central nervous system
- the peripheral nervous system
what forms the central nervous system
the brain and spinal cord
what forms the PNS
the nerves that connect the spinal cord to the rest of the body
what does the CNS do
controls most of the functions and responses in the body
what does the PNS do?
it forms the somatic nervous system which detects & responds to stimulus outside the body
how do we respond to an environment
can be voluntary or involuntary
how does a response work
- receptors detect stimulus
- impulse sent along the sensory neutron to the spinal cords
- CNS integrates the information and sends to the brain if necessary for processing prior to initiating a response
- impulse is sent from the CNS along the motor neuron to effector
- effector generates response
what is an effector
glands or muscles (things that cause response)
what is the autonomic nervous system apart of
the PNS
what regulates the autonomic nervous system
hypothalamus
what is the ANS made up of
parasympathetic
sympathetic
what happens in the parasympathetic
eyes - constrict pupil
salivary glands - stimulates salivation
heart - slows heartbeat
lungs - constrict bronchi
stomach - stimulates digestion
liver - stimulates bile release
intestines - stimulates peristalsis and secretion
bladder - contracts bladder
what happens in the sympathetic
eyes - dilate pupil
salivary glands - inhibit salivation
heart - accelerates heartbeat
lungs - dilates bronchi
stomach - inhibits digestion
liver - stimulates glucose release
kidneys - stimulates epinephrine and norepinephrine release
intestines - inhibits peristalsis and secretion
bladder - relaxes the bladder
what do the sensory organs do
play a vital role in the system, sensing changes to the environment surrounding the animal
what are the types of receptors
chemoreceptor
thermoreceptor
mechanoreceptor
photoreceptor
what are receptors
they detect stimuli and change due to stimuli, they can lead to action potentials in sensory neurons that are attached
what are the sense receptors
auditory
somatosensory
olfactory
gustatory
visual
what’s the somatosensory receptor
the skin contains variety of receptors which respond to the temperature, touch, pressure (whiskers contribute)
what’s the olfactory receptor
in the nasal cavity respond to odour molecules in the air, some animals have a Jacobsons organ which detects moisture borne odour molecules using the flehmens
what’s the gustatory receptor
tongue of many animals contain papillae which have taste buds, they respond to chemicals in food and drink to give sensations of taste - not all animals perceive taste the same way
what’s the visual receptor
photoreceptors in the retinal layer of the eye respond to the light
what’s the auditory receptor
hair cells in the inner ear vibrate according to the pitch and volume of sounds, they send impulses via auditory nerve to brain for processing
how do the receptors work in the eye
they are sensitive to light stimuli and send visual signals to the brain through the nervous system
describe the cornea and the purpose
its the transparent covering on the eye and it protects the eye, helping converge light rays that enter the eye
describe the retina and the purpose
its the layer of light sensitive cells at the back of the eye and it detects light rays that are focused by the cornea and lens
describe the iris and the purpose
its a ring of muscles around the pupil, coloured which provides eye colour and it controls the amount of light entering the eye
describe the lens and the purpose
its transparent, flexible and can change shape due to the ciliary muscles and focuses the light onto the retina and focuses on objects
describe the optic nerve and the purpose
its a bundle of fibres that relays information from the retina and fovea to the brain
explain the vision process
the light rays are refracted and focus on the pupil as they enter through the cornea. muscles in the iris contract and relax to control the amount of light passing through the pupil. the lens refracts the light more so it is focused on the retina, the photoreceptors in the retina respond to the energy from the light and generate action potentials which are sent along the optic nerve to the brain for processing
what are the photoreceptors
they are the primary layer to the retina and consist of rods and cones
what are rods in photoreceptors
very light sensitive and can function in the dark, they have a single pigment (rhodopsin) which cannot detect colour so vision is grey. they have a low level of visual sharpness as many rod cells share connection with optic nerve
what are the cones in photoreceptors
function at a higher intensity than rods and allow some species to see in colour and contain photo pigments (iodopsin) which respond to colour. each cone responds to one colour, the range of colours detected depends on the types of cone cells present. they give a high level of visual sharpness as each cone has a single connection to the optic nerve
what does the use of light do in the photoreceptors
when light is detected by rods, rhodopsin is broken down into 2 proteins (opsin and retinal) via bleaching which causes depolarisation giving a rise to action potential which is transmitted via optic nerve to the brain. rhodopsin is generated slowly so cone cells provide visual information when light levels are high due to inability to regenerate effectively
what are the eye adaptations for a nocturnal animal
- much larger eye with wider pupils allowing more light to be captured
- much higher conc of rod cells
- slit pupils as they are easier to contract
- have tapetum lucidum.
explain the role of the tapetum lucidum
its a reflective pigment which aids sight in dark conditions, it improves vision in low light as it maximises the available light by reflecting it back through the photoreceptors, stimulating more receptor cells
what vision do carnivores have
binocular - eyes are positioned at the front of the face creating a narrower field of vision and able to focus as have better depth perception
what vision do herbivores have
monocular - eyes positioned on side of the head creating a wider field of vision which is good for detecting predators but they have poor depth perception
explain degenerative myelopathy
disease that effects the spinal cord. it is degenerative and gets worse with time.
symptoms - wobbling, loss of coordination, nerves get affected and communication is lost
no treatment but managed by good husbandry and health management
explain listeriosis
bacterial infection which can cause encephalitis (swelling on brain) , abortions and blood poisoning
symptoms - disorientation, facial paralysis, constant salivation, collapse and involuntary movement
if untreated can lead to death
what is the PNS made up of?
receptors - sensory (afferent) & motor (efferent)
what happens when a receptor is stimulated?
it gets sent to the CNS - spinal nerves are connected to spinal cords & cranial nerves to brain
explain the spinal cord
its a long bundle of nerves which branches out between the vertebrate to different parts of the body - connects brain to PNS
what is the CNS surrounded by?
shock absorbing fluid (cerebrospinal fluid)
how is the CNS kept separate to rest of body fluids?
blood brain barrier
what does the blood brain barrier do?
protection of changes in blood, toxins and pathogens.
what is the blood brain barrier made up of?
specialised cells which line blood vessels of capillaries in region of CNS.
what does the parasympathetic do?
rest & digest response which restore normal functioning after extra stimulation in sympathetic system is done
what does the sympathetic do?
fight or flight response which prepares the body for physical activity - neurotransmitter = noradrenaline
what does the chemoreceptor do?
detect presence of chemicals
what does the thermoreceptors do?
detect change in temperature
what does mechanoreceptors do
detect mechanical changes in environment
what do photoreceptors do?
detect light
describe the eyelid and its purpose
its the fold of the skin which covers the eye & it cleans and protects the eye
describe the sclera and its purpose
its the white part of the eye made of tough collagen fibres & it provides protection & support
describe the vitreous humour and its purpose
its located behind the lens & it gives the eyeball its shape
describe the choroid and its purpose
layer of blood vessels with a black pigment & it nourishes the eye and absorbs light
describe the pupil and its purpose
its the hole in the middle of the iris & it controls the amount of light entering the eye
describe the ciliary body and its purpose
its attached to the underside of the lens & it produces aqueous humour and helps with focusing by altering shape of the lens
describe the aqueous humour and its purpose
found behind the cornea & helps keep its rounded shape and provides nutrients to cornea and lens
describe the lateral rectus muscles & its purpose
they are found on lateral side of the eye & help orientate the pupil away from centre of the body
describe the medial rectus muscle and its purpose
found on medial side of eye and help orientate the pupil towards centre of the body
describe the fovea and its purpose
spot located in the macula which has a high density of cone cells, it gives sharp central vision & light is focused on this spot by the lens
describe the optic disc and its purpose
its the blind spot where there are no photoreceptors & its where the optic nerves leave the eye
