Nervous system Flashcards
(87 cards)
1
Q
whats the function of the nervous system
A
”- Receive stimuli from external and internal environments
- Conduct impulses and coordinate an appropriate response
- Integrate activities of other systems”
2
Q
what are the types of NS and their components
A
”- Central NS: Brain, Spinal cord
- Peripheral NS: Sense organs, Peripheral Nerves”
3
Q
how does the nervous system respond to stimuli
A
“1. Reception – sensory receptors in the sense organs detect stimuli (change in internal/external environment) and initiate an electrical impulse (action potential)
2. Transmission – of electrical impulse from neurone to neurone to the CNS
3. Integration – sorting and interpreting signals
4. Action – by an effector (muscle or gland)”
4
Q
how is the CNS protected
A
“protection via
- Skull – bone- hard protection (brain)
- Vertebrae bone- hard protection (spinal cord)
- Meninges – 3 layers of membrane (dura- hard, arachnoid- weblike, pia- delicate)
- CSF – Cerebrospinal fluid shock absorbing fluid (also acts as medium for exchange for nutrients, etc, between blood and brain)”
5
Q
whats the role of the brain and spinal cord in the CNS
A
“Brain:
- Receiving impulses from sensory receptors
- Integrating & correlating incoming info
- Sending impulses to effector organs
Spinal cord
- Transmit impulses to and from brain
- Relay action potentials between sensory organs & effector organs (in reflex actions)”
6
Q
describe the Peripheral NS and its divisions
A
“Includes paired spinal nerves and cranial nerves
Can be divided into:
- Somatic nervous system
- Autonomic nervous system
- Peripheral nerves consist of bundles of axons of sensory and motor neurones (nerve fibres) surrounded by connective tissue and glial cells
- Afferent (sensory) nerve fibres transmit signals towards the CNS
- Efferent (motor) nerve fibres transmit signals away from the CNS (eff off)
- Both somatic and autonomic nervous systems have afferent and efferent pathways”
7
Q
describe the somatic nervous system
A
”- eacting to external environment/stimuli
- Under conscious/voluntary control
- Detect change using sense organs
- Sensory neurone relays information from sensory receptor to CNS
- Motor neurone relays message from CNS to effector i.e. skeletal muscle”
8
Q
describe the autonomic nervous system and its pathways
A
“nvoluntary response to internal stimuli. E.g. heart rate, vasoconstriction/dilation, breathing, digestion etc.
efferent pathway consists of
- sympathetic nervous system
- “Fight or flight”
- Mobilise energy
- E.g. increased heart rate, increased heart force, reduced digestion
- parasympathetic nervous system
- “Rest and digest”
- Activated when at rest – recuperation after stress response
- Conserve or restore energy
9
Q
what are the types of neurones
A
”- Sensory neurone
- Collects sensory information
- Transfers information to the CNS
- Motor neurone
- Transfers nerve impulse from CNS to muscles
- relay neurone
- Connect one neurone to another
- Found in CNS”
10
Q
whata are some examples of sensory neurones, their sense, location and the energy received
A
“Photorecepotors- sight- eye- light
Chemoreceptors- taste/smell- mouth/noes- chemical potential
Mechanoreceptors- touch/hearing- skin/ear- kinetic”
11
Q
whats the differenvce between innate and conditioned reflexes + e.gs
A
“innate- withdrawal reflex- response to pain
conditioned- scratching reflex-
- A dog will scratch rhythmically with one hind-leg in response to an irritant stimulus”
12
Q
describe the steps to generating an action potential
A
”- Begins at Resting potential (-70mV)
- Depolarisation, Na+ voltage gated channels open rapidly- potential difference increases (outide becomes more positive than inside), if enough positive charge enters, then we might pass a threshold (-55mV)- triggers AP
- Repolarisation, Na+ channels close and Potassium channels open, K+ moves in, reducing potential differece
- Hyperpolarisation, more K+ leaves than Na+ enters - -90mV
- Refractory period- after hyperpolaristaion, potential diff returns to resting, at this point, Na+ is inside and K= is outside and this must be returned to normal to generate another action potential”
13
Q
how is resting potentila established and maintained
A
“-70mv
- The Na+/K+ pump pumps 3 Na+ out and 2K+ in. Most of the K+ is found inside the cell and most Na+ is inside
- But K+ will also leak out of the cell via facilitaed diffusion as the membrane is more permeable to K+ (there are more K+ channels in the membrane than Na+).
- As the K+ leaks out it causes the membrane to polarise. It will be become more negative inside the cell compared to outside.”
14
Q
why is the refractory period important
A
”- Ensures unidirectional propagation
- Prevents overfiring of action potentials- no excessive nuerone activity-normal brain function and preventing seizures.
- encoding information, shorter refractory period allows a neuron to fire more rapidly, which may be important for encoding high-frequency signals. Conversely, a longer refractory period may be important for encoding lower-frequency signals.”
15
Q
what is the all or noting response
A
“The size of the impulse is independent of the size of the stimulus:
If the intensity of a stimulus is below the threshold potential, no action potential will be initiated. aph
But If it is above threshold then an AP will happen. The intensity of the stimulus is coded by the frequency of APs.”
16
Q
what are the factors that affect speed of a nerve impulse
A
”- myelination
- axon diameter
- temperature”
17
Q
how does myleination increase speed of an imopulse across the axon
A
”- Ion channels present at the nodes of Ranvier allow the movement of sodium and potassium ions across the membrane. It is at these points that an action potential can be generated in a myelinated neurone.
- The action potential moves from node to node. This is referred to as saltatory conduction and is much quicker than the step-by-step conduction that occurs in a non-myelinated neurone.”
18
Q
how does axon diameter affect the speed of nerve impulses
A
Action potentials are conducted quicker along axons with bigger because there is less resistance to the flow of ions than in cytoplasm of a smaller axon. With less resistance the ions diffuse faster and propagation at next part of neurone is quicker.
19
Q
how does temperature affect the speed of nerve impulses
A
the speed of conduction increases as the temperature increases. Ions move faster (greater kinetic energy) as the temperature rises . But if the temperature gets higher than 40C than proteins would start to denature
20
Q
what is hypokalaemia
A
”- Hypokalaemia- too little potassium
- Hypokalemia increases the resting potential (i.e., makes it more negative) and hyperpolarizes the cell
- induce dangerousarrhythmias.”
21
Q
what the role of synapses
A
”- ensures one way transmission
- increases the range of responses to a stimulus
- summation”
22
Q
whats the cause, mechanism, clinical signs and treatment of Botulism toxin
A
“Cause:
- Caused by the bacteria Clostridium botulinum
- Anaerobic bacteria found in the soil
- Toxin ingested in contaminated feed: canned food, silage
Mechanism:
- The toxin acts at the presynaptic membrane and prevents ACh release
Clinical signs:
-Ruminants particularly susceptible, dead birds /rodents are usually the source.
- Progressive flaccid paralysis
- Muscular weakness
- Sternal recumbency
- Loss of tone in tail
- Protruding tongue
- Laboured breathing
- Post mortem, presence of bacteria or toxin in Gastrointestinal tract (GIT)
Treatment;
- Supportive: fluids, feeding, turning
- Antitoxin: expensive, efficacy
- Antibiotics – not effective
- Euthanasia due to welfare issues
Prevention
- vaccine not generally available yet in the UK – only used under special treatment certification
- Feed analysis – food borne”
23
Q
whats the causes, mechanisms, effexts and treatment of organophosphate
A
“Causes:
- Insecticide drugs eg. diazinon
- Sheep dips, flea and mange treatments
Mechanism:
- AChE (competitive) inhibitors which leads to increased ACh in the synapse and muscles
- acts as a non-competitive inhibitor to Acetylcholinesterase so Ach is not broken down
Effects:
Rare in small mammals
- Headaches
- Tiredness
- Muscle aches
- Anxiety, changes in personality
- MCS
- Large doses: collapse, respiratory distress, dysrhythmia
Treatment:
- Prevent further exposure
- Supportive
- Atropine
- Pralidoxime chloride”
24
Q
define cataract
A
A cataract is an opacity of the lens or its capsule and often gives the eye a cloudy appearance
25
define glaucoma
"if drainage of aqueous humor is impaired the pressure in the eyeball is increased- bulges, a condition known as glaucoma
- Aqueous humor supplies the avascular cornea and lens with nutrients and removes waste
- It also helps the eyeball to maintain shape"
26
wha are the causes and treatment of cataracts
"Causes- diabeteic dogs, age,
Treatment- can only be treated by surgery, phacoemulsification removes material from inside the lens, small corneal incisions remove the cataractous lens through a small opening created, and high-frequency ultrasonic waves are used to carefully break the cataract into small fragments which are then removed by means of irrigation"
27
causes and treatments of glaucoma
"causes- family history, age, ocular hypertension
treatment- prescription eye drops, laser treatment, lowers ye pressure fluid drains, surgery"
28
whats the vestibular system - ear
"- controls balance and tries to prevent an animal falling over.
- the balance system consists of sensors (located deep inside the ear in the inner ear) and a specialised control centre (located at the back of the brain)"
29
whats the anatomy and role of of the semicircular canals
"- Each semi-circular canal has one bulbous shaped end called an ampulla and is filled with fluid called endolymph
- - In the ampulla is a structure that is called the **gel-cupula.**
- There are multiple sensory hairs cells projecting into the gel of the cupula (the stereocilia)
- When the head changes position fluid in the canal pushes the cupula, bending it. This causes the hair cells to bend and creates APs"
30
how does rotational movement work in the ear
"- head changes positon so the endolymph flows against the movement- inertia
- The cupula gets pushed or pulled during angular movement from the flow of endolymph, causing the cupula to bend. Sensation triggered"
31
what are the steps to depolarisation of the hair cells in ear- signal transduction
"1. The surrounding extracellular fluid, the **endolymph** has a **high concentration of K+.** This is not like other parts of nervous system where the concentration K+ outside the cell is lower.
2. The depolarisation is brough about by bending of the hair cell, which opens **mechanically-gated** K+ channels.
3. The K+ **influx** depolarises the cell.
4. As this occurs **voltage gated Ca2+ channels** open.
5. Results in exocytosis of the neurotransmitter **glutamate**.
- Glutamate creates excitatory post synaptic potentials in sensory neurone which opens sofium gated channels and Impulse travels along nerve fibres that form the auditory nerve"
32
what are the 2 otolithic organs in the ear and describe them
"- the utricle and saccule.
Utricle (horizontal): If we start moving forward the inertia dense otoliths will bend the hair cells backwards. This creates an impulse telling us forward acceleration
Saccule (vertical): If we were in a lift and the lift starts moving up. The inertia of the otoliths pulls bends the hair cells downwards. This creates an impulse telling us about acceleration in the vertical plane."
33
whats the role and anatomy of the otoliths
"- on top of the gel are sprinkles of “ear stones” like sprinkles on ice cream. These are **otoliths** … ear rocks. (CaCO3).
- Both utricle and saccule detects acceleration and motion and transmit this information to the brain via the **vestibulocochlear nerve**. then move the oppositw way of movement"
34
whats the role of the outer ear
"- From pinna to tympanic membrane (ear drum)
- The pinna, the visible part of the ear, is shaped like a funnel. This structure helps to collect sound waves from the environment and direct them into the ear canal."
35
whats the role of the middle ear
"needs sound amplification
- sound collected by pinna>ear canal
- Sound waves cause pressure change as oval window is much smaller than the tympanic cavity
Amplification achieved
1. Surface Area Difference: Ear drum has an area of 0.6cm2. The oval window is much smaller , about 0.032cm2. Reducing the area increases pressure exerted on the window
2. The Mechanical advantage of the bones These bones act as a Type 1 lever system, transferring vibrations from the eardrum (tympanic membrane) to the oval window (the membrane-covered opening to the cochlea). The lever action increases the force of the vibrations while maintaining their frequency."
36
whats the role of the inner ear
"- the middle of the cochlear contains the basilar membrane
- It vibrates in response to sound, with different regions tuned to specific frequencies (high frequencies near the base, low frequencies near the apex).
1. Stapes foot transmits pressure waves to perilymph
2. Causes the basilar membrane to bend.
3. The basilar membrane will bend most at the place that the vibration has the greatest resonance.
4. Low frequency sounds bend the basilar membrane at the apex
5. High frequency sounds bend the membrane closer to the start"
37
how many motor nuerones dles somatic nervous system have compared to automatic
"Somatic has 1 motor nuerone and myleinated
autonomic has 2 motor nuerones and is not myleinated"
38
how is the sympathetic system organised
"- Ganglions located just outside the CNS
- Ganglia in a chain each side of spinal cord.
- Sympathetic chain ganglia
- Short pre-ganglionic nerve fibres
- Synapse with many post-ganglionic fibres
- In a number of ganglia
- (or synapse with prevertebral ganglia...or direct innervation of adrenal medulla)
- Endocrine association"
39
how is the parasympathetic system organised
"- Pre-ganglionic fibres are LONG
- Ganglia are in target organs/adjacent to the wall
- Ganglia NOT inter-connected
- No endocrine association
- Action more localised than sympathetic system
- Post ganglionic synapses use acetyl choline as neurotransmitter"
40
name the nerve fibre, its nuerotransmitter and its desigmation
"Pre-G SNS - Acetylcholine- Cholinergic
Post-G SNS- Noradrenaline
(Norepinephrine)- Adrenergic
Adrenal medulla- Adrenaline (Epinephrine)- Adrenergic
Pre-G PSNS- Acetylcholine- Cholinergic
Post-G PSNS- Acetylcholine- Cholinergic"
41
What is the role of the autonomic nervous system in animals
"Maintenance of homeostasis
- Blood pressure control
- Body temperature
- Internal pH
- Blood oxygen and carbon dioxide
- Work through negative feedback mechanisms"
42
whats the function of the cornea
transparent lens that refracts light as it enters the eye
43
whats the function of the iris
controls how much light enters the eye
44
lens function
transparant disc that can change shape to focus light on the retina
45
retina function
contains light receptor cells - rods and cones
46
optic nerve function
sensory nuerone carries impulse from eye to brain
47
describe binocular and monocular vision
"- **Binocular** (stereoscopic) vision occurs when both eyes are used to view the same object
- Better detail and depth perception
- Image appears three-dimensional
- Predator species
- **Monocular** vision refers to animals which use each eye independently
- Birds and lizards
- Greater field of vision
- some animals use both, eg horses"
48
describe the effect on the pupil in dim and bright lighting
"DIM: pupil dilates, circular muscles relax, radial muscles contract and its controlled by SNS
BRIGHT: pupil constricts, circular muscles contract, radial muscles relax, controlled by PSNS"
49
how does the lens help to focus light rays on the fovea
"refraction-As light moves from one medium to another its speed and therefore direction changes
- the lenses concave shape allows for refreaction to occur and make one focal point"
50
what does refraction depend on
"- the distance of the light source from the eye
- curvature of the lens"
51
what does accomodation mean in relation to focusing the eye
"Accomodation
- the eye can alter its focus to form clear images of both close and distant objects on the retina
- Achieves this by altering the shape of the lens
- Lens shape can be altered by suspensory ligaments and the ciliary muscles.
- This adjusts the focus of the image on the back of the retina"
52
how does accomodation enable animals to focus on distant objects
"**Distant**
- Ciliary body relaxed
- Suspensory ligaments taught
- Lens under tension
- Lens flatter"
53
how does accomodation enable animals to focus on near object
"- Ciliary body contracted
- Suspensory ligaments relaxed
- Lens free to take its own shape
- Fatter lens"
54
whats the pathway ofrods and cones to the brain
"- Rods and cones generate a neural signal
- Rods and cones both form synapses with bipolar cells
- Bipolar cells in turn synapse with sensory neurons called ganglion cells.
- The axons of the ganglion cells cover the inner surface of the retina - combine to form the optic nerve"
55
whats the distribution of rods and cones
"- There are no sensory cells where the optic nerve leaves the eye…blindspot
- Rods and cones are unevenly distributed
- **Area centralis:** Region where the concentration of sensory cells are highest, especially cones.
- **Fovea***…*in middle of area centralis with highest density of cones. In humans it contains only cones."
56
describe cone cells
"- Respond to light at higher intensities so less sensitive
- Allow perception of fine detail
- Colour vision as have varying sensitivity to light of different wavelengths
- Each cone synapses to one bipolar cell which in turn synapses to one ganglion cell – so each has its own pathway to the CNS- **spatial** **summation**"
57
describe rod cells
"- Function in dim light (scoptic vision) as very sensitive
- Allow detection of shape and movement
- Not colour sensitive
- many rods make synapse with one bipolar neuron - **temporal**"
58
what does rhodopsin consist of
"- **opsin**: a protein
- **retinal**: a reversibly bound cofactor produced in cells from Vitamin A"
59
describe retinal
"- **Retinal is key to the light reaction** and the initiation of the nerve impulse.
- All **photopigments contain retinal** (differences in properties of photopigments due to variation in opsin)
- Retinal is a long molecule"
60
describe the process of bleaching in retinal
"- When it is bound to opsin it has an angular (folded) shape (***cis-*configuration**)
- When retinal absorbs light, it straightens due to change in the bonding (to the ***trans-*configuration**) and no longer fits into the opsin molecule (becomes cleaved)
- process is called bleaching"
61
describe the process of bleaching in rhodopsin when here is a light stimulus vs when there isnt
"**When there is light stimulus**
- Rhodopsin molecules absorb light, change conformation and retinal separates from opsin (a process known as bleaching)
- Once cleaved it cannot continue to absorb more light
- In bright light most rhodopsin molecules are bleached
**When there is no light stimulus**
- Enzymes convert retinal back to *cis* form
- Retinal can then recombine with opsin to make rhodopsin
- This is called dark adaptation
- requires more time than bleaching
- this explains why you are initially ‘blind’ when you walk from bright sunlight into a darkened room"
62
describe visual acuity and how it comes about
"*The ability of the eye to resolve two or more points that are separated spatially*
- Cones are responsible for high visual acuity
- each cone synapses to one bipolar cell which in turn synapses to one ganglion cell – so each has its own pathway to the CNS
- Each part of an image is detected by a different cone cell
- This acuity would be lost if more than one cone was to share the same sensory pathway- convergence
- Fove ha most cone cells (**FO**r **VE**ry **A**cute Vision)"
63
describe colour vision and how it comes about
"- There is only one type of rod
- rods are unable to provide information about the wavelength of light that stimulates the retina
- There are functionally different types of cone cell, all contain photo pigment… photopsin
- each has a different form of **opsin**
- they have sensitivity to light of different wavelengths.
- Humans have three different types of cone
- a specific wavelength of light will lead to a given *ratio* of the degree of stimulation of blue, green and red cones.
- By comparing the stimulation of different types of cone, the human brain can detect a wide range of colour"
64
What is the gross structure of the brain
- meninges
- forebrain (prosencephalon)
- midbrain (mesencephalon)
- hindbrain (rhombencephalon)
- brain stem
- spinal cord
65
Name the features of the prosencephalon with brief descriptions
- Telencephalon (cerebrum)
- cerebral cortex: two hemispheres
- Corpus callosum [connects two hemispheres
- Rhinencephalon: includes oflactory bulbs
- Diencephalon
- thalamus,
- hypothalamus,
- pituitary gland)
66
Name the features of the Rhombencephalon
- Metencephalon (cerebellum and pons)
- Mylencephalon (medulla oblongata)
67
What are the meninges and describe its features
- Thin layer of tissue between the brain and the inner skull
- dura mater- tough outermost layer, closely applied to the inner table of the skull
- arachnoid,- thin layer closely applied to the dura mater
- pia mater- very thin layer applied to the surface of the brain
68
What is the structure and function of the surface of the brain
- Gyri- raised bits
- Sulci- Grooves between gyri
- Gyrocephalliac- folding
- role of increasing surface area so more neurons so increased brain ability to process information.
69
What are the 4 ventricles of the brain
1 + 2: Lateral ventricles in each brain hemisphere
3: Connects the lateral ventricles
4: Runs down the spinal cord or into the subarachnoid space
70
what are the brain ventricles and whats their purpose
- They are a network of interconnected cavities filled with CSF
- cushions the brain, removes waste, delivers nutrients
71
What is the corpus callosum and its role
- connects the left and right cerebral hemispheres, facilitating communication and coordination between them.
- It is the largest white matter structure in the brain
72
what are the four lobes of the brain
- At the front the **frontal lobe**
- At the back the **occipital lobe**
- At the top the **parietal lobe**
- At the bottom the **temporal lobe**
73
what are the three functions of the cerebrum
- relay station for sensory information (vision, somatosensory/touch, taste/gustation, smell/olfaction, audition/sound)
- planning and initiating motor activity
- cognitive processes like thinking, judging and problem solving
74
what is the frontal lobe responsible for
- reasoning
- emotions
- problem solving
- recieves olfactory senses (smell)
- Receives gustatory senses (taste)
75
What is the parietal lobe responsible for
- orientation
- perception of somatosensory stimuli (touch)
76
what is the temporal lobe responsible for
- recognition of auditory stimuli
- memory,
- speech
77
what is the occipital lobe responsible for
visual processing
78
what is the function of the hypothalamus
- keeps your body in a stable state called **homeostasis**
- Releasing hormones: E.g. ADH
- Regulating body temperature = thermoregulation
- Regulating water balance = osmoregulation
- Controls sexual response
- Controls hunger
79
what hormines does the hypothalamus release
- Thyrotropin releasing hormone
- Corticotropin releasing hormone
- Gonadotropin releasing hormone
- Growth hormone releasing hormone
- Antidiuretic hormone
- Oxytocin
80
what is the function of the cerebellum
responsible for coordinating movements and balance
81
how does the cerebellum differ in species
- The relative size of the cerebellum differs greatly between species
- Animals that fly and swim have much larger cerebellums compared to animals that do not
82
what is the functoon of the medulla oblongata
- regulating several basic functions of the autonomic nervous system including:
- respiration,
- cardiac function,
- vasodilation
- reflexes like vomiting, coughing, sneezing, and swallowing.
83
What is transmissible spongiform encephalopathies
- They are prion diseases- infectious
- they are involved cell division of neurones and homeostasis of neurone cell number, cell signalling and are also involved in cell to cell adhesion. The infectious agent that is a prion disease is a **misfolding** of this normal prion into a **PcPsc** – the diseased prion.
84
What are the causes of transmissible spongiform encephalopathies
- caused by prions- misfolded proteins.
- Random mutation of the prion DNA. This spontaneously creates misfolded prion proteins.
- Interaction between the normal prions and the misfolded prions is thought to convert the normal prions into misfolded prions. If the misfolded prions are not spontaneously generated by mutation then normal prions could come into contact with misfolded prions that have been ingested.
85
what are the clinical signs of transmissible spongiform encephalopathies
- Microscopically we see **lesions** or **holes** created inside of the brain tissue. This gives the brain matter a **sponge like** appearance
- after death a biopsy of brain tissue can be taken and immunohistochemistry can be used to identify prion proteins
86
signs of bovine spongiform encephalopathies in cows
- apprehension or nervousness (flighty)
- repeated, exaggerated reactions to touch or sound
- weakness or high stepping of the legs, particularly the hind legs
- reluctance to cross concrete or drains, turn corners or enter yards or go through doorways
- aggression towards humans or towards other cattle
- manic kicking during milking or reluctance to allow milking
- head held low
87
What affect did BSE have on british farming during the 1990s and why
- ban on selling beef between 1997 and 1999
- EU had a 10 year ban on exporting british beef
- incineration of 1 million cattle
belived that eating beef from an infected cow would lead to the human pyro disease (CJD)- leads to early dementia, mutism and akinetic
