Nervous System- Exam Bs Flashcards
What are antibiotics?
Drugs that for that infection against bacteria.
Bactericidal antibiotics- kill bacteria by changing the structure of the cell, wall or cell membrane , or by distrusting the action of essential enzymes
Eg. Penicillin
Bacteriostatic antibiotics- stop bacteria from reproducing, usually by distrusting protein synthesis, preventing metabolic process ie. cell respiration, altering nucleus acid
Eg. Tetracycline
What antivirals?
Drugs that work against viral infections. They inhibit the development of viruses (inactivate). Viral proteins are disabled by specifically designed chemicals. Preventing viruses from entering cells, synthesis of viral genome and prevent release of virus.
Eg. Inferferons
What is homeostasis?
Maintainance of a constant internal environment
Eg. Temperature, body fluids, ion concentration, glucose and blood pressure
What are the components of a feedback loop?
Stimulus Receptor Modulator Effector Response Feedback (pos or neg)
What are the 6 types of receptors?
Thermoreceptors- heat and cold
Osmoreceptors- detect change in osmotic pressure
Chemoreceptors- detect change in blood oxygen and carbon dioxide
Pressoreceptors- detect change in blood pressure changes (skin)
Baroreceptors- detect changes in blood pressure
Nocireceptor- respond to damaging or potentially damaging stimuli, pain receptor
Nature of message in nervous system and endocrine system?
N system- electrical impulses and neurotransmitters
E system- hormones
Transport of message in nervous system and endocrine system?
N system- along membrane of neuron
E system- by the bloodstream
Cells affected in nervous system and endocrine system?
N system- muscles and gland cells; other neurons
E system- all body cells
Types of response by nervous system and endocrine system?
N system - usually local and specific
E system- may be general and widespread
Time taken to respond with nervous system compared endocrine system?
N system- rapid ( within milliseconds)
E system- slower ( seconds to days)
Duration of nervous system and endocrine system responses?
N system- brief ( stops quickly when stimulus stops)
E system - longer lasting ( may continue long after the stimulus has stopped)
What are reflexs?
Rapid and autonomic responses to a change in the environment. They are coordinated by the spinal cord on an involuntary bandits. Once the reflex has occurred, an impulse is sent to the brain and the person becomes aware of the situation.
4 important properties of reflexes?
- Stimulus
- Involuntary and rapid
- Small no. Of neurons involved
- Stereotyped (same way each time)
What route does the reflex arc take?
- Sensory receptor detects stimulus and generates nerve impulse in a sensory neuron (pain= nociceptor)
- Sensory neuron carries impulse into the spinal cord via the dorsal root ganglion and Dordal root
- Impulse transmitted into an interneuron in the grey matter of spinal cord
- Interneuron transmits impulse to a motor neuron. Motor neuron carries impulse out via the ventral root to the effector.
- Effector responds to remove the stimulus
- While reflex is being carried out, an impulse is sent to the brain so an individual becomes aware of the situation. Upper sensory neuron carries the message.
What is the hole in the middle of the spinal column grey matter called?
Central canal
What is the dorsal route ganglion?
A group of cell bodies ( somas)
What are protective reflexes?
- born with them Eg. Sneezing, coughing, blinking
- protect the body from injury
- up spinal cord only
What are acquired reflexesa.
- reflexes learnt through constant repetition.
Eg, maintenance of balance while riding a bike, jamming brakes on car to avoid dangerous situations or flinching when ball is coming
What is the nervous system?
Communication network and control center of body. It is involved in maintenance of homeostasis inside the body, a task it shares with the endocrine system
What is the central nervous system?
Control centre consisting of brain and spinal cord
What is the peripheral nervous system?
Nerves that connect central nervous system with the receptors, muscles and glands
What are neurons?
Nerve cells which are the basic structural and functional units of whole nervous system
What is myeline sheath?
Layer of fatty material that covers axons and increases speed of nerve impulse.
What is an axon?
Long extension of nerve fibres from cell body
What are dendrites?
Short extension of cytoplasm of cell body. They Often have many branches, receive messages from other neurons and carry them towards the cell body.
What is the cell body?
Soma: contains nucleus and many other organelles
What is node of Ranvier?
Interval of gaps along the axon
What are schwann cells?
The cell that wraps around a nerve fibre forming the myelin sheath
What shoe of neurons are receptors found on?
Sensory only
Functional neurons?
Sensory, motor and inter neurons
What are sensory neurons?
Receptor neurons that carry messages from receptors in the sense organs or skin to the CNS
What are motor neurons?
Neurons that carry messages from CNS to the muscles and glands- the effectors
What are interneurons?
Association, relay or connector neurons located in the CNS and are links between sensory and motor neurons
What are the structural neuron types?
Multipolar- 1 axon, multiple dendrites
Bipolar- 1 axon and 1 dendrite
Unipolar- 1 axon extension and cell body to one side of it.
What is a nerve fibre?
Any long extension of cytoplasm for a nerve cell body
What is a nerve?
Bundle of nerve fibre held together by connective tissue
What is a synapse?
Junction between branches of adjacent neurons. Messages are passed across the synapse.
What are nerve impulses?
-Electrochemical charge that travels along nerve fibre.
Where does a Nerve impulse start?
The dendrite
How does nerve impulse generation start? (Breif)
- Resting neuron contains POTENTIAL ENERGY. This comes from the difference between the electrical charge on the inside and outside of a neuron.
- Nerve impulse = ACTION POTENTIAL
A change in the EXtracellular fluid and intracellular fluid generates an impulse that propagates ( moves) along neuron.
~The nerve impulse undergoes polarisation, depolarisation, repolarisation, and hyperpolarisation~
What happens at the polarisation stage of nerve impulse generation?
there is a positive EF (due to sodium) &a negative IF (due to large - proteins).
RESTING MEMBRANE POTENTIAL= -70mv
potassium readily diffuses through cell membrane into EF. The Na/ K pump actively pumps potassium back into cell.
What happens at depolarisation of nerve impulse generation?
- a stimulus opens some Na+ voltage gated channels and Na+ moves into cell causing cell to become positive .
- when membrane potential reaches -55mv an all or none response occurs
- all Na+ voltage channels open in that area causing an influx of Na+ = positive IF
What happens at Repolarisation stage, of nerve impulse generation?
- Charges return to positive EF & negative IF
- Na+ ions diffuse through IF causing in adjacent parts of the neuron to depolarise. Na+ also stimulates k+ voltage gate channels to open.
- k+ moves out of the cell into the EF making it more positive. Thence IF is - charged ( large - proteins) and Charges are restored
- This process of repolarisation generates ACTION POTENTIAL which stimulates the Na+ V.G channel in adjacent areas to open.
the Na+/ K+ pump restores ionic distribution Na+ out and K+ in. While the cell segment is restoring back to polarised state. It is in REFARACTORY PERIOD. This prevents the neuron from being stimulated again and prevents the nerve impulse from travelling backwards
What happens at the hyperpolarisation stage of nerve impulse generation?
- the charges at this point are more negative than resting ( in the cell?) causing K+ V.G to close
- K+/Na+ pump is restoring the ionic distribution
- cell is in refractory period and cannot be restimulated and the nerve impulse is prevented from moving backwards
What are the 2 ways nerve impulses travel along a neuron?
Saltatory conduction- mylinated conduction
Continuous conduction- unmylinated conduction
Describe process of saltatory conduction?
- nerve impulses Jump from one node to the next, allowing nerve impulses to travel much faster
- it jumps from nodes because nerve fibres are insulated from the extracellular fluids at the nodes of ranvier and ions cannot flow between the inside and outside of the cell membrane and action potential cannot form.
Describe process of continuous conduction?
- Each action potential generates another action potential just in front of it, this repeats along the length of the whole membrane
- depolarisation in one area of the membrane causes a local current flow between neighbouring areas on the membrane.
What is a neuromuscular junction?
Junction between branches of a motor neuron and a muscle fibre; also called the motor end plate
What is a synapse?
- At Junction between branches of adjacent neurons there is a gap called the synapse.
- most occur between the end of branch of an axon of one neuron and dendrite or the cell body of another neuron.
Messages are passed across the synapse
How does transmission occur across a synapse?
- Action potential causes depolarisation of axon terminal membrane, causing calcium V.G channels to open causing calcium to enter the cell.
- Calcium ions bind to the synaptic vesicles which contain neurotransmitters. These vesicles move and then bind to the presynaptic membrane allowing neurotransmitters to be released via exocytosis into synaptic cleft
- Neurotransmitters diffuse across the cleft and bind to receptors.
i.e sodium ligand channels
Protein channels open causing sodium to enter the cell causing depolarisation of post synaptic membrane - Action potential probates through post synaptic membrane. Neurotransmitters are broken down and removed from receptor mediated proteins.
i. e Aceylcholinenesterase breaks down Acetylcholine into Acetyl CoA and chlorine. Acetyl coa and chlorine are then recycled, taken up into the cell via endocytosis and converted back into acetylcholine at the axon terminal
What are the protective features of the CNS?
Skin
Periosteum
Bone
Duramater, Arachnoid, Pia mater (meninges)
How does skin protect the CNS?
Outermost protective layer
How does periosteum protect the CNS?
Below the skin, layer of protective tissue that surrounds bone
How does bone protect the brain?
- Skull. Brain is protected by the cranium which houses the brain
- vertebrae or vertebral column.
What is the order of the meninges?
Duramater (outer)
Arachnoid
Piamater
Describe duramater?
Pain sensitive, has own blood supply, sticks closely to bones of skull but on inside of vertebral Canal is not so close fitting, tough and fibrous, Toughest outermost layer of meninges
Describe arachnoids?
- middle layers
- filled with web of collagen
- has cerebral fluid
- no blood vessels
- contains CSF
Describe Pia mater?
- sticks closely to surface of brain and spinal cord
- very tender
- rich supply of blood vessels which provide nutrients to nervous tissue
- helps produce CBF
Where is Cerebrospinal fluid found?
Occupies space between inner and middle layer of meninges. Circulated through cavities in brain and through a canal in center of spinal cord.
What does cerebrospinal fluid do?
protection: acts as shock absorber
Support: brain floats in it
Transport: takes nutrients to brain cells and spinal cord, removing wastes
Describe parietal lobe of cerebrum?
- It is in between the frontal and occipital lobe
- primary sensory strip and association area
- processes tactile information, pain etc.
Describe frontal lobe?
- front of the brain
- judgement, emotions, motivation and memory, categorising, thinking and expressive language, reasoning
- Primary motor cortex
- responsible for voluntary control of muscles
Describe occipital lobe?
- Helps with vision
- behind the parietal lobe
Describe temporal lobe?
- olfactory (smelling) and auditory areas
- speech auditory processing
- processing of emotional responses
Physical features of cerebrum?
- largest part of brain
- divided into four lobes
- cerebral cortex is its outer layer
- below cerebral cortex is white matter
- convoluted surface
Features of cerebral cortex
2-4cm thick
- outer surface of cerebrum
- grey matter
Function of cerebral cortex?
Higher order functions such as thinking, reasoning, memory, learning and conscious awareness of surroundings
Physical features of corpus callosum?
- wide band of nerve fibres that lie underneath cerebrum at the base of the longitudinal fissure
- nerve fibres cross from one cerebral hemisphere to another allowing communication between sides
Function of corpus callosum?
Communication between two hemispheres
Physical features of thalamus?
- Large
- dual lobed
- mass of grey matter
- beneath cerebral cortex
Function of thalamus
- directs nerve impulses to correct parts of brain
- relate sensory motor signals to cerebral cortex
- receives auditory and visual signals
Physical features of hypothalamus?
- middle of the brain, can’t be seen from outside
- small
Function of hypothalamus?
- involved in homeostasis
- eg, regulation of autonomic nervous system ( regulation of heart rate, blood pressure etc.)
- regulation of body temp, food and water intake, patterns of waking and sleeping and control of urinary bladder
Physical features of pituitary gland
- ductless
- middle of the base of skull
- pea sized
- below hypothalamus
Function of pituitary gland?
- secretes hormones directly into bloodstream and produces hormones for various bodily functions
Physical features of pons?
- part of brain stem
- a bulge
Function of pons?
- message station that directs Impulses
- relays signals from forebrain to cerebellum
- has sensory soles in hearing, taste and facial sensations
Physical features of spinal column?
- roughly cylindrical in structure
- extends from the large opening at the base of the skull to the second lumbar vertebrae
- about 44cm
- enclosed in vertebrae canal and bone
- cross section shows grey matter at center surrounded by white matter (g matter is H shape )
Function of spinal column?
- Carry sensory impulses up to brain and motor impulses down from brain
- integrate certain reflexes (fast automatic responses)
Physical features of cerebellum?
- under rear part of cerebrum
- second largest part of brain
- surface folded into series of parallel ridges
- outer folded part is grey matter
- inside is white matter that branches to all parts of cerebellum
Function of cerebellum?
- under rear part of cerebrum
- second largest part of brain
- surface folded into series of parallel ridges
- outer folded part is grey matter
- inside is white matter that branches to all parts of cerebellum
Physical features of medulla oblongata?
- continuation of spinal cord
- 3cm long
- extends from where spinal cord enters skull
- nerve fibres pass through going to and from parts of brain
Function of medulla oblongata?
Cardiac centre- regulates the rate and force of heart rate
Respiratory centre- controls rate and depth of breathing
Vasomotor centre- regulates diameter of blood vessels
+ others they regulate reflexes of swallowing, sneezing and vomiting.
- centres are controlled by higher centres in the brain.
Speed of saltatory conduction and continuous conduction?
Saltatory = 140 m/s Continuous = 2 m/s
What is the function of the Autonomic
Adjustment of the internal environment
Homeostasis
Function of the somatic division?
Response to the external environment
Effectors is the Autonomic division!
Heart muscles, involuntary muscles and glands
Effectors of the somatic division?
Skeletal (voluntary) muscles
In the Autonomic nervous system, where does the efferent pathway lead?
To nerve fibres from the CNS to the effector with a synapse in a ganglion
In the somatic nervous system, where does the efferent pathway lead?
One nerve fibre from the CNS leas to the effector and there is no synapse or ganglion
What neurotransmitters are involved in the Autonomic division?
Acetylcholine and noradrenaline
What neurotransmitters are involved in the somatic division?
Acetylcholine
Is the Autonomic division involuntary or voluntary
Usually involuntary
Is the somatic division involuntary or voluntary
Usually voluntary
What type of nerves go to the target organ in Autonomic division?
Sympathetic and parasympathetic
What type of nerves go to the target organ in somatic division?
Only one set of nerves (sensory?)
Effect of autonomic division on target organs?
Excitation and Inhibition
Effect of somatic division on targe organs?
Always excitation
What parts of the brain are responsible for regulating the ANS?
Groups of nerve cells in medulla oblongata, hypothalamus and cerebral cortex
What is a neurotransmitter?
Molecules thw carries a nerve impulse across a small gap between branches of adjacent nerve cells,
Where are neurotransmitters released from in the somatic and autonomic divisions?
Somatic- synapse
ANS- ganglion
What are the two afferent pathways?
—SENSORY ( towards CNS)—-
Somatic sensory: info from skin and muscles
Visceral: information from internal organs
What are the two efferent pathways?
—motor division (away from CNS)——
Somatic division: sends impulses to skin and muscles
Autonomic division: sends impulses to involuntary muscles
What are the divisions of the Autonomic division?
Sympathetic- controls body when active, fight of flight. It’s a longer neuron pathway so it’s the slower system
Parasympathetic- controls body when resting, quiet. Very short neurons, faster system
What neurotransmitters are released by the parasympathetic and sympathetic divisions?
Parasympathetic- acetylcholine
Sympathetic- noradrenaline
Before getting to CNS impulses must pass through…..?
Peripheral nervous system, and be transported by interneurons to CNS
