Nervous System Flashcards
what are coordinating systems
systems that allow communication between the receptors and the effectors of the body so that correct reactions to any change in the environment can be brought about
what two systems work together to respond to changes in the environment and control conditions inside the body
- nervous coordinating system - responds fastest and is brought about by impulses traveling along nerves
- endocrine coordinating system - slower and is brought about by chemicals called hormones which are carried in the blood
what is the nervous system
it is the body’s control and communication centre. it provides a continuous flow of information between the environment, the brain and the different parts of the body. this enables the body to function in an orderly and effective way and to perform all the everyday tasks such as eating, running, solving a problem, controlling emotions such as fear etc.
how does the nervous system function
- sensory function - sensory receptors detect the changes in the external environment and the environment within the organism
- integrative function - the central nervous system receives this information and decides which effectors need to react to the stimulus
- motor function - effectors (muscles and glands) bring about the appropriate responses
what are stimuli
physical or chemical changes in the environment that are capable of causing a response in an organism
gives examples of stimuli in the environment
- light
- temperature
- sounds
- atmospheric pressure
gives examples of stimuli inside our bodies
- blood pressure
- blood pH
- tension in muscles
what is the human nervous system divided into
- Central nervous system
2. Peripheral nervous system
LABEL THE CENTRAL AND PERIPHERAL NERVOUS SYSTEM
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what is the CNS made up of
a concentrated mass of interconnected neurons (nerve cells) grouped together to form
- brain
- spinal cord
what is the CNS responsible for
processing information coming from our senses, keeping our organs and reflexes functioning and directing our movements, thoughts and feelings
how is the CNS protected
- the extremely soft and delicate brain and spinal cord tissue is protected and nourished by three connective tissue membranes called the meninges
- the layer between the 2nd and 3rd layer of the membrane is filled with cerebro-spinal fluid which acts as a cushion, protecting the CNS against shock and damage
- the whole CNS and it’s meninges are enclosed within the bony case made up of two separate structures
- the cranium
- the vertebral column
• other factors such as the S-shaped curvature of the spine, the cartilaginous discs between the vertebrae and joints of the lower limbs all prevents jarring of the CNS
LABEL THE PROTECTIVE LAYERS OF THE CNS
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what is the brain
the enlarged, upper part of the spinal cord, enclosed in a bony cranium
describe the brain (3 points)
- it’s like a mushroom, the cap of the mushroom being the cerebrum snd then stalk being the brain stem
- at the back near the top of the brain stem is a bump, the cerebellum
- the lower part of the brain stem is known as the medulla oblongata
LABEL THE EXTERNAL AND INTERNAL VIEW OF THE BRAIN
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what is the largest part of the brain and what is it divided into and by what
the cerebrum, it is divided into two cerebral hemispheres by a longitudinal fissure
what holds the hemispheres of the brain together
a mass of myelinated nerve fibres, bundled into large tracts that form the corpus (body) callosum (white)
what does the corpus callosum provide for
communication between the cerebral hemispheres and between the cerebral cortex and lower parts of the CNS, which enables them to function as a coordinated whole
what is the surface of the cerebrum made up of
a large number of folds (gyri) and grooves (sulci) that enlarge the surface area so that a large amount of brain cells can fit into a small cranial cavity
what are ventricles in the brain
they’re 4 cavities in the centre of the brain that are filled with cerebro-spinal fluid
what is the cerebral cortex
the outer 3 mm of the cerebrum.
what forms grey matter
the collection of cell bodies of neurons which form the cerebral cortex (the greyness is due to the grey appearance of cytoplasm which is called neuroplasm in neurons)
what makes up white matter
a collection of myelinated nerve fibres (the whiteness is due to the fatty myelin)
what are the functions of the cerebrum
- the motor area (frontal lobe) is where all the voluntary moments of the body originate. we’re able to consciously control our voluntary moments that are brought about by the contraction of muscles
- the sensory areas that receive and interpret impulses from the sense organs. eg.
- heading, tasting, smelling (temporal lobe)
- sight (occipital lobe)
- skin sensations (parietal lobe) - the association cortex is involved with the higher mental activities such as intelligence, memory, perception, language and consciousness. collectively the function of the association areas is to sort out, integrate and store info before it’s sent to the motor areas. eg.
- anger, aggression (frontal lobe)
LABEL THE LOBES OF THE CEREBRUM
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describe the cerebellum
- it lies behind and below the cerebrum
- made up of two hemispheres and has shallow surface folds
- a feature of the cerebellum is the arrangement of the white matter and grey matter. the white matter looks like branches of a tree and is surrounded by grey matter which looks like the foliage - hence the name tree of life
what are the functions of the cerebellum
it receives sensory input from the motor region of the cerebrum, the eyes, muscle spindles and the organs of balance in the ears
- it processes this info and uses it to coordinate the actions of the voluntary muscles so that complicated physical actions can be performed in a smooth controlled way
- it is partly responsible for controlling muscle tone
- using info from the inner ear, it helps to maintain posture and balance
where do we find the hypothalamus
below the thalamus and above the pituitary gland
what are the functions of the hypothalamus
- control the autonomic system and therefore play an important role in maintaining homeostasis by regulating
- body temperature
- water balance and thirst
- food intake
- sleep cycle - it is the centre for emotional response and behavior eg. has nuclei involved in the perception of
- pain, pleasure, fear and rage
- biological rhythms and drives eg. sex drives - it controls the functioning of the pituitary by:
- secreting hormones eg. ADH, which is stored in the posterior lobe of the pituitary
- controlling the release of all the hormones from both lobes and pituitaries
where’s the medulla oblongata
it forms the lowest part of the brain stem and passes through the foramen magnum at the base of the cranium, it is known as the spinal cord
what are the functions of the medulla oblongata
- servers as the pathway for impulses to and from the brain
- it acts as a reflex centre controlling reflexes such as
- breathing
- heart beat
- blood pressure (by regulating vasodilation and vasoconstriction)
- swallowing and peristalsis - it also controls less important reflexes such as sneezing, coughing, hiccuping and salivating
why do the hemispheres of the brain control opposite sides of the body
because nerve fibres between the spinal cord and brain cross over in the medulla oblongata
what is the spinal cord
an elongated rod of nervous tissue that extends from the medulla oblongata through the foramen magnum
how long is the spinal cord
approximately 45 cm
LABEL THE SPINAL CORD
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WHAT IS:
- vertebra column
- vertebrae
- vertebral canal
- discs of cartilage
- spinal cord
- central canal
- the backBONE
- 33 individual bones stacked on top of one another
- hollow tube formed in the vertebral column by the 33 stacked vertebrae
- cartilage occurring between the vertebrae to stabilize and allow for bending
- runs in the vertebral canal and is made up of nervous tissue
- runs through the spinal cord and is filled with cerebro-spinal fluid
structure of the spinal cord
- has an H shaped central area of grey matter (made up of nerve cell bodies, dendrites and synapses)
- white matter surrounds the grey (made up of axons with myelin sheaths)
- central canal at centre of grey matter
- the spinal cord is divided into eight and left sides by two grooves
- a pair of spinal nerves enter and leave the spinal cord between the successive vertebrae (there are 31 pairs of spinal nerves)
- each spinal nerves has a dorsal root that enters the grey matter, a ventral root that leaves the grey matter
- a collection of neuron cell bodies creates a ganglion in the dorsal root
what are the functions of the spinal cord
- served as a pathway for nerve impulses from the receptors to the brain and the brain to the effectors
- it has an integrative function in that it is the seat of primitive reflex actions called spinal reflexes which serve to protect the body, eg. bladder reflex, knee jerk reflex
LABEL A CROSS SECTION THROUGH THE SPINAL CORD
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what does the PNS consist of
all nervous tissue outside the PNS
what is the PNS made up of
nerves that link the CNS to the receptors and effectors to the body, ie. 43 pairs of nerves:
- 12 pairs of cranial nerves (connected to the brain) these may be sensory (afferent), motor (efferent) or mixed nerves. they leave the brain and conduct impulses to and from the sense organs and muscles in the head and face
- 31 pairs of spinal nerves which enter snd leave the spinal cord between the vertebrae. these are all mixed nerves being made up of motor and sensory nerve fibres
what are the functions of the PNS
- collect info form receptors and transmit this info by the way of impulses along sensory, afferent neurons to the CNS - sensory functions
- to transmit impulses from the CNS by way of motor, efferent neurons to effectors to bring about an appropriate responses - motor function
how is the motor division made up
- somatic nervous system - conducts impulses from the CNS to skeletal muscles and therefore controls all voluntary muscular movements
- autonomic nervous system - conducts impulses from the CNS to cardiac muscle, smooth muscles and glands and therefore controls the functioning of involuntary muscles and glands
what is the autonomic nervous system largely involved with
keeping a blacked internal environment ie. maintaining homeostasis
what is the ANS made up of
- the parasympathetic nervous system
2. the sympathetic nervous system
what are the functions of the parasympathetic and sympathetic nervous systems
- sympathetic nervous system works together with the hormone adrenalin in emergency situations that cause stress and require the ‘fight or flight’ state. stimulation by these nerves need more oxygen, glucose and blood being sent to the skeletal muscles where cellular respiration is sped up to release more energy for action
- parasympathetic nervous system enables the body to recover from sympathetic stimulation and turn back to normal
give examples of things that the parasympathetic and sympathetic nervous system do
- speeds up and slows down heart and respiratory rate
- adjusts blood pressure and body temperature
- shunts blood to stress where it’s most needed
- increases or decreases digestive secretions
the responses are involuntary and always happening
what is double innervation and antagonistic (in terms of parasympathetic and sympathetic nervous system)
double innervation - the fact that most organs are innervated by nerve fibres from both systems
antagonistic - the effects produced by each system are opposed by one another
what is nervous tissue
tissue consisting of neurons and neuroglia
describe neurons
firstly they form the structural units of the nervous system
• in the correct conditions they can function for a lifetime
• they cannot undergo mitosis so they cannot be replaced if destroyed (however stem cells may be used to replace damaged neurons)
• they have a high metabolic rate and need co tikis supplies of oxygen and glucose to survive
what are neuroglia
they are supporting cells to the neurons, they play a critical role in making myelin and supporting and protecting neurons
neuron = nerve cell glia = glue
describe the structure of neurons
neurons are made up of the same basic parts as any other animal cell, including a cell body made up of a cell membrane, cytoplasm, cell organelles and a nucleus
in addition to this they have long the
in processes which are fibres of cytoplasm that extend from the cell body - these make it possible for nerve impulses to be carried long distances
what are the fibres in a typical neuron
- Dendrites - they conduct impulses towards the cell body. They are short, tapering processes that branch extensively to provide a large surface area to receive signals from other neurons
- Axon - they conduct impulses away from the cell body. Each neuron has a single axon although certain axons may give off branches along their length. an axon usually branches extensively at its end to form terminal branches
Name of the different types of neurons
- sensory/unipolar neuron
- connector neurons (also known as the relay neuron association neurons or interneurons)
- Motor/multipolar neuron
Explain sensory neurons
they are afferent neurons as they carry impulses from receptors towards the central nervous systems (CNS) where the sensation is interpreted
af = towards unipolar = one fibre attached to the cell body
explain connector neurons
these are multipolar neurons found in the CNS and make up 99% of neurons of the body. They receive impulses from the sensory neurons and pass them on to other neurons
multipolar = many fibres attached to the cell body
explain motor neurons
these are efferent neurons as they carry impulses away from the CNS to the effectors so that the appropriate response can be brought about
ef = away
LABEL AND ANNOTATE A DIAGRAM OF A MOTOR NEURON
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LABEL THE DIAGRAM SHOWING THREE TYPES OF NEURONS
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what direction do nerve impulses always travel in a neuron
from the dendrites to the cell body and then down the axon
what are nissl granules
groups of ribosomes in the neuroplasm that are involved with protein synthesis
what are neurilemma
a collective name for the outer sheath made up of Schwann cells
what are schwann cells
the things wrapped around the axon several times. the inner concentric layers of fatty tissue fuse to form the myelin sheath
DRAW A MULTIPOLAR AND UNIPOLAR NEURON
LOOK AT SLIDES
what are nerves
bundles of neurons in the PNS
what are tracts
bundles of nerves in the CNS
describe the structure of a nerve
a nerve consists of a large number of neuron fibres
(neuron fibres = cytoplasmic processes that extend the cell body of all neurons, ie. axons and dendrites)
- neurons are bound together into bundles by connective tissue called the perineurium
- inside the nudges the neurons are surrounded by delicate connective tissue called the endoneurium
- the entire nerve is surrounded by a sheath of connective tissue called the epineurium
- an artery and a vein occur between the bundles to nourish the fibres and remove waste
LABEL THE DIAGRAM OF SECTION THEOUGH A NERVE
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what are the functions of nerves
to carry impulses from the receptors to the CNS and from the CNS to effectors to bring about appropriate responses
what is a nerve impulse
a minute electrical signal - a wave of depolarization which is caused by a stimulus and creates a difference in electrical charge across the membrane of a nerve fibre
the stimulus can be mechanical, chemical, thermal or electrical
how are nerve impulses transmitted
nerve impulses are carried along a nerve fibre as follows:
•RESTING POTENTIAL
- a neuron is in a resting state when it’s not being stimulated and it’s membrane is polarized (ie. the outside of the membrane is + and the inside is -)
- the resting potential is the difference in the charge (voltage) across the cell membrane
• ACTIVE POTENTIAL
- The active state involves the conduction of nerve impulses along a neuron in response to a stimulus
- When a neuron is stimulated, the distribution of negative and positive ions on either side of the cell membranes changes, resulting in a rapid reversal of changes (the inside of the cell becomes + and the outside becomes -) this process is called depolarization
- if the stimulus is strong enough ie. above a certain threshold potential, complete depolarization results in a burst of electrical activity which passes along the length of the neuron as nerve impulses
- this is known as the all or nothing repose as if the threshold potential is not reached, no nerve impulses are generated
• REFRACTORY POTENTIAL
- this is the recovery stage as the membrane becomes repolarized when an impulse has passed along
- this is brought about by carrier molecules that actively transport the ions back through the membrane to their original positions
- the membrane is returned back to its resting potential ready for another stimulus
what gives neurons that special conducting properties
the difference in the mentanes permeability to Sodium and Potassium ions
LABEL THE DIAGRAM OF ACTION POTENTIAL
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what are synapses
the junction which a nerve impulse passes from an axon terminal to a neuron, a muscle cell or a gland cell
what can be found in the cytoplasm of synaptic knobs
hundreds of small vesicles filled with molecules of a neurotransmitter such as the chemical acetylcholine
what is a neurotransmitter
a chemical substance released from axon terminals at a synapse to carry impulses across the gap
how to impulses travel across synapses
- when never impulses reach the terminal branches of axons, they cause vesicles in the pre-synaptic membrane of a synaptic knob to burst, releasing neurotransmitters which diffuse across the synaptic gap
- the neurotransmitters carry impulses across the gap - a chemical process which stimulates receptors in the post synaptic membrane to initiate nerve impulses
LABEL A DIAGRAM OF IMPSE CONDUCTION AT A SYNAPE
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what is a myoneural synapse
the synapse between the terminal branches of a motor neuron and a muscle
how do general anesthetics wolf
they temporarily inhibit an impulse being generated in post synaptic membranes
why are synapses important (3)
- they make sure that the flow of impulses is in one direction only as the vesicles containing the transmitter are in the axon terminal knobs only, so impulses can only be transmitted from one side
- they allow the dispersal of impulses to many other neurons as the neurotransmitter can stimulate several post synaptic membranes
- they allow the filtering out of continual, unnecessary or unimportant stimuli. if a neuron is constantly stimulated (eg. clothes touching the skin) the synapse will not be able to renew its supply of transmitter fast enough to continue passing the impulse across the cleft, so these stimuli are filtered out
what is a reflex arc
the functional unit of the nervous system. it is the pathway followed by impulses from a receptor to an effector to bring about a reflex action
what two types of relaxes are there
- somatic - activates the skeletal muscles
2. autonomic - activates the smooth or cardiac muscle and glands
where are reflexes centers situated
in the brain (sneezing, blinking, breathing) and spinal cord (withdrawal of a hand or foot when touching something hot)
what is the importance of a reflex arc
- to enable the body to respond quickly to stimuli as very often higher centered if the brain are not involved
- to provide inborn safety mechanisms which serve to protect the body from danger
give examples of reflexes
- sneezing to clear the nasal passage of irritants
- blinking when danger threatens the sensitive tissue of the eyes
- yawning when there’s too much CO2 in the blood
- coughing when food enters the trachea
what 5 essential components to basically all somatic reflexes have
- receptor -skin (responds to stimuli and generates impulse)
- sensory - neuron (carries impulse to the CNS)
- connector - neuron (acts as reflex centre)
- motor - neuron (carries impulse to an effector organ)
- effector - muscle (brings about change)
