Nerves & The Nervous System Flashcards
Give some reasons why we have a nervous system.
Diffusion is too slow beyond the cellular level.
For rapid, precise data transfer.
Effective over long distances.
Evolved in response to the evolution of movement.
Hormonal signals are too slow.
The are approximately 10^? neurons and 10^? neuroglia in the human brain?
There are approximately 10^11 neurons and 10^12 neuroglia in the human brain.
What cells can be described as neural glue.
Neuroglia.
Which neurones are the largest cell body bound by a plasma membrane?
Motor neurones.
What part of a neurone can also be called the soma or perikaryon?
The cell body.
There are high numbers of which organelle in the cytosol of neurones?
Mitochondria.
Why are there large numbers of mitochondria in the neuronal cytosol?
To provide the ATP needed for the energy to maintain the charge separation across the plasma membrane which makes neurones electrically excitable.
Where in a neurone would you find Nissi Substance?
What is it?
Adjacent to the nucleus.
Nissi substance is a dense area which contains rough endoplasmic reticulum where proteins are assembled and folded.
Neurone have lots of what in their rough endoplasmic reticulum in the cytosol, to synthesise proteins and polypeptides.
Ribosomes.
Which two organelles in neurones have these functions?:
Lipid and steroid synthesis, Ca2+ uptake and storage, protein modification and sorting.
Smooth endoplasmic reticulum and golgi complex.
Name the organelle:
Found in the cytosol of neurones, they have hydrolytic enzymes for breakdown and disposal.
Lysosomes.
Name the organelle:
Found in the cytosol of neurones, they detoxify in oxidative reactions.
Peroxisomes.
What do proximal and distal mean?
Proximal - close to the cell body.
Distal - distant from the cell body.
What is the function of dendrites?
Dendrites receive incoming signals via receptor proteins. They increase surface area.
How many dendrites can each neurone have?
a. 10,000.
b. 140,000.
c. 400,000.
c. 400,000.
Can dendrites generate signals?
Yes, some dendrites can generate signal output and communicate with other neurones.
Where in the neurone is an action potential generated?
Axon hillock.
What point can be called the origin of the axon?
Axon hillock.
The dendrites can be divided into dendritic branches then dendritic spines. Altogether these can be referred to as…?
…the dendritic tree.
What is the myelin sheath?
A fatty layer of insulation which increases the speed of conduction of action potentials.
What cells make up the myelin sheath?
Neuroglia.
Are all neurones myelinated?
No.
There are gaps between myelinated segments of the axon, which the signal ‘jumps’ between. What are they called?
The Nodes of Ranvier.
What are axon terminals also known as?
Boutons or variscosities.
Which part of a neurone can be between one micrometre and 25 micrometres in diameter and from micrometres to metres long?
The axon.
What is the ‘unit’ of neurone excitability?
Action potential.
At resting membrane potential, is the distribution of ions on either side of the membrane even or uneven?
Uneven.
When an action potential is received by the dendrites, the ………………. of the membrane reverses briefly, passing information to the axon terminals by ……………………….. of the membrane.
Polarity, depolarisation.
What are the three types of synapse called?
Axondendritic, axosomatic and axoaxonic.
Which part of two neurones meet at an axondendritic synapse?
Dendrite to dendrite.
Which part of two neurones meet at an axosomatic synapse?
Axon terminal to dendrite.
Which part of two neurones meet at an axoaxonic synapse?
Axon terminal to axon terminal.
Which type of synapse is most common?
Axodendritic (dendrite to dendrite).
Which type of synapse is more influential?
Axosomatic (axon terminal to dendrite).
Which type of synapse influences the release of neurotransmitters?
Axoaxonic (axon terminal to axon terminal).
………………… transmission happens at the synapse, …………………… transmission happens along the axon.
Chemical, electrical.
Lots of …………….. are present at the synapse, which show as darker areas on an electronmicrograph?
Proteins.
What can be excitatry, inhibitory or both, depending on the receptor?
Neurotransmitters.
Name the three main groups of neurotransmitters and give some examples.
Amino acids - glutamate, glycine, gamma-aminobutyric acid (GABA).
Amines - adrenaline, noradrenaline, serotonin (5-HT), dopamine, acetylcholine.
Peptides - Substance P, neuropeptide Y, somatostatin, dynorphin, cholecystokinin and enkephalin.
Amino acid and amine transmitters are found in …………………… vesicles.
Synaptic.
Peptide neurotransmitters are found in ………… ………… vesicles.
Dense core.
True or false? A neurone can only contain one type of neurotransmitter.
False. One neurone can contain a number of different neurotransmitters.
In a chain of neurones, does EVERY neurone need to be excited for an action potential to be generated?
Yes.
For ………………… to take place and an action potential to be generated, …………….. neurone in a chain needs to be excited.
Integration, every.
What is a synapse en passant?
A synapse that is not right at the end of an axon (i.e. axon terminals), but the occur at swellings along the length of the axon.
Are synapses unidirectional?
Yes, mostly.
Dense core vesicles contain ………………. neurotransmitters and are also known as ………………….?
Peptide, secretory granules.
How wide is the synaptic cleft (in nm)?
20nm-50nm.
Give examples of what a post-synaptic structure could be.
A muscle, the dendrites of another neurone.
What happens to neurotransmitter once it reaches the axon terminal?
It binds to vesicles, which diffuse across the synaptic cleft and bind with receptor proteins on the post-synaptic structure.
Dendrites can receive excitatory AND inhibitory effects at the SAME time. For integration to take place and an action potential to be generated, what condition must be met?
Excitiation must outweigh inhibition for an action potential to be generated.
True or false? A dendrite can only receive an excitatory OR an inhibitory signal at any one time?
False. A dendrite can receive excitatory and inhibitory signals at the same time. For an action potential to be generated the excitatory signal must outweigh the inhibitory signal.
The greater the number of action potentials, the more …………………… is released.
Neurotransmitter.
Define convergence.
Multiple input onto an individual neurone.
Define divergence.
Individual neurone output onto many others.
In a single-celled organism, such as an amoeba, which part of the cell functions as the ‘brain’?
The nucleus.
A hydra is an example of a multicellular organism which has a ‘brain’ composed of a network of intercommunicating nerve cells called…?
…a ‘nerve net’.
What is the evolutionary process called whereby organisms became bilaterally symmetrical around the midline, giving them ‘front’ and ‘back’ ends?
Cephalisation.
Cephalisation lead to organisms having which key part of the nervous system as we recognise it in multicellular organisms today?
Spinal cord.
In the evolution of the nervous system, what did longitudinal centralisation do?
Segmentation - aggregation of nerve cell bodies into ganglia, with neurones projecting to and from each ganglion. This co-ordinates the function of body segments within that region. This decentralised brain function.
At which stage of the evolution of the nervous system did brain function become decentralised as nerve cells aggregated into ganglia?
Longitudinal centralisation.
What are the three main types of neurone?
- Afferent.
- Efferent.
- Interneurones.
Which neurones take information from a receptor towards the ‘control centre’?
Afferent neurones.
Which neurones take information from the control centre towards an effector?
Efferent neurones.
Which neurones form central connections?
Interneurones.
Which neurones take information TOWARDS the control centre? Which take it AWAY?
Towards - afferent.
Away - efferent.
Name the neurone:
Branched axon with no dendrites. Usually afferent neurones. Often has one end in CNS, one end at sensory receptors. Cell body somewhere in the middle.
Unipolar / pseudounipolar.
Name the neurone:
Have an axon AND dendrites. Mostly found in the retina.
Bipolar.
Name the neurone:
Has an axon and several dendrites. Usually efferent neurones. Often found in the somatic nervous system, i.e. as motor neurones.
Multipolar.
Which type of neurone is usually afferent, and which is usually efferent? Unipolar or multipolar?
Afferent - unipolar.
Efferent - multipolar.
Which division of the nervous system is made up of the brain, brain stem and spinal cord?
The central nervous system.
The central nervous system contains millions of which type of neurone?
Interneurones.
Which division of the nervous system contains everything that is NOT found in the central nervous system, i.e afferent neurones, efferent neurones?
The peripheral nervous system.
Are afferent and efferent neurones found in the central nervous system or the peripheral nervous system?
The peripheral nervous system.
How many pairs of spinal nerves are there?
31.
What are the FIVE types of spinal nerves?
Cervical, thoracic, lumbar, sacral and coccygeal.
Why do some animals have more coccygeal nerves than humans?
Animals with tails have more coccygeal nerves than humans.
Name the spinal nerves:
8 -
12 -
5 -
5 -
1 -
8 - cervical.
12 - thoracic.
5 - lumbar.
5 - sacral.
1 - coccygeal.
How many pairs of cranial nerves are there?
12.
Name the twelve pairs of cranial nerves.
HINT: ‘On Old Olympus’ Towering Top, A Friendly Viking Grows Vines And Hops’.
Optic
Olfactory
Oculumotor
Trochlear
Trigeminal
Aducens
Facial
Vestibulocochlear
Glossopharyngeal
Vagus
Accessory
Hypoglossal.
Which of these cranial nerves are sensory nerves, which are motor nerves and which are both?
Optic
Olfactory
Oculumotor
Trochlear
Trigeminal
Aducens
Facial
Vestibulocochlear
Glossopharyngeal
Vagus
Accessory
Hypoglossal.
HINT: ‘Some Say Marry Money, But My Brother Says Big Brains Matter Most’.
Optic - somatic
Olfactory - somatic
Oculumotor - motor
Trochlear - motor
Trigeminal - both
Aducens - motor
Facial - both
Vestibulocochlear - somatic
Glossopharyngeal - both
Vagus - both
Accessory - motor
Hypoglossal - motor.
What are the two divisions of the peripheral nervous system?
Somatic and autonomic.
Does the somatic nervous system detect and respond to the external environment or the internal environment?
The external environment.
Where are the afferents and efferents of the somatic nervous system?
Afferents - skin, joints, muscles etc.
Efferents - skeletal muscles.
Does the autonomic nervous system respond to the external or internal environment?
The internal environment.
Which division of the peripheral nervous system maintains homeostasis and controls endocrine function?
The autonomic nervous system.
Where are the afferents and efferents of the autonomic nervous system?
Afferents - internal organs.
Efferents - smooth / cardiac muscle, glands.
What are the two divisions of the autonomic nervous system?
Sympathetic and parasympathetic.
Is the ‘fight or flight’ response controlled by the sympathetic or the parasympathetic nervous system?
The sympathetic nervous system.
Is the ‘rest and digest’ state controlled by the sympathetic or the parasympathetic nervous system?
The parasympathetic nervous system.
What happens in the body when the parasympathetic nervous system is active?
Pupils constrict, saliva becomes more watery, mucus production increases, heart rate and blood pressure lowers, lungs are contracted, gastric juices are secreted and motility increases, increased digestion in the small intestine, increased secretions and motility in the large intestine, urine secretion from the kidneys increases and the bladder walls are contracted with the sphincter relaxed.
What happens in the body when the sympathetic nervous system is active?
The pupils dilate, saliva thickens, mucus production decreases, heart rate and blood pressure increase, lungs are relaxed, peristalsis decreases in the stomach, motillity decreases in the small intestine AND the large intestine, the kidneys secrete less urine and the bladder wall is relaxed with the sphincter closed.
How many neurones are there in an efferent in the autonomic nervous system? And how many in the somatic nervous system?
Autonomic nervous system - TWO neurones.
Somatic nervous system - ONE neurone.
Each efferent in the autonomic nervous system has two neurones. What is the difference between efferents in the parasympathetic and sympathetic nervous systems?
Parasympathetic nervous system - short post-ganglion, long pre-ganglion.
Sympathetic nervous system - long post-ganglion, short pre-ganglion.
In which division of the autonomic nervous system is the efferent short pre-ganglion and long post-ganglion?
The sympathetic nervous system.
In which division of the autonomic nervous system is the efferent long pre-ganglion and short post-ganglion?
The parasympathetic nervous system.
Which neurotransmitter is released by somatic motorneurones? What is the effector tissue?
Acetylcholine is released into skeletal muscle.
Efferents in the parasympathetic nervous system release which neurotransmitter?
Acetylcholine.
Acetylcholine, noradrenaline and adrenaline can all be released by efferent in which division of the autonomic nervous system?
The sympathetic nervous system.
Which of these ANS efferents have ganglia?
Sympathetic
Parasympathetic
Somatic motorneurone
Sympathetic and parasympathetic.
Are the ganglia of the sympathetic and parasympathetic nervous system INSIDE or OUTSIDE the spinal cord?
Outside.
