Nervous system Flashcards
List the components of the central nervous system (CNS).
The spinal cord and the brain.
List the components of the peripheral nervous system (PNS).
the 12 pairs of cranial nerves and the 31 pairs of spinal nerves
divisions of the PNS
the afferent and efferent division
What does the afferent division do?
- it houses receptors which take info into the CNS.
- somatic sensory neurons are in the skin and muscle
- visceral snesory neurons are found in internal organs
What does the efferent/motor division do?
- it carries info away from the CNS to effectors;
- houses the somatic division and the autonomic division
What is the role of the efferent somatic division?
It is to carry impulses from the CNS to any voluntary skeletal muscle
What is the role of the efferent autonomic division?
- to send impulses from the CNS to any involuntary muscles e.g. the stomach/heart
- controls the parasympathetic and sympathetic divisions
it is a highly specialised cell which transmits electrical messages across the body at high speeds
What is the function of a nerve cell?
it is a highly specialised cell which transmits electrical messages across the body at high speeds
What does the cell body do in a neuron?
it organises the cell, houses the nucleus, mitochondria and other organelles
What are dendrites?
fairly short extensions of the cytoplasm which carry nerve impulses into the cell body of another neuron
What is an axon?
a singular and long extension of the cell body in which the impulse travels along to reach the axon terminal
Schwann cells
cells that form the myelin sheath around the axon by wrapping and layering itself around, creating many layers of insulation.
Why is this insulation needed?
To ensure nerve impulses travel fast and don’t die out along the axon.
The myelin sheath
composed of a layer of Schwann cells and a neurilemma which acts to:
- insulate the axon;
- protect it from damage; and
- speed up the movement of impulses along the axon.
What is an axon terminal?
the end terminals of an axon which create synaptic conjunctions with other dendrites.
What are nodes of Ranvier?
little breaks in the myeling sheath where nerve impulses jump from one to another to increase conduction rate.
The three types of neurons (function)
- sensory neurons - afferent and carries impulses from sense organs to the CNS;
- motor neurons - efferent and carries impulses from the CNS to muscles/glands; and
- interneurons - association/connector/relay neurons which are located in the CNS and link sensory and motor neurons together.
The three types of neurons (structure)
- multipolar - motor neurons/interneurons;
- bipolar - eye/ear sensory neurons and interneurons; and
- unipolar - sensory neurons.
what are thermoreceptors?
- sensitve to changes in temperature.
- peripheral/skin - detect changes in the skin’s temperature and report back to the brain and either hot or cold.
- central - detect changes in the body’s core temperature.
osmoreceptors
- located in the hypothalamus.
- detects changes in the osmotic pressure in the blood and bodily fluids.
chemoreceptors
- located in the mouth, nose, and carotid/aortic bodies.
- detects unwanted chemicals in the body e.g. CO2/O2.
- internal ones detect changes in the composition of bodily fluids.
mechanoreceptors
- touch receptors.
- lighter movement detections are found in heavier concentrations on the surface of the skin.
- ones found under the skin detect vibrations and forceful movement.
nociceptors
- pain receptors
- stimulated by tissue damage.
- concentrated in skin and mucous membranes, but not found in the brain.
- very little adaption - pain will continue as long as the stimulant is present (keeps us aware).
How is an electrical impulse created?
By rapid movements of sodium and potassium ions across a cell membrane, depolarising it and creating a short-lasting electrical charge.
Define a nerve impulse
A combination of waves of action potential travelling along a nerve fibre.
Describe the resting membrane of a nerve fibre.
- positive charge on the outside due to a high Na+ concentration.
- negative charge on the inside due to a high amount of K+ ions, but a larger amount of other negatively charged ions.
Define potential difference
the difference in electrical charge between two points and the amount of energy their separation can release.
Membrane potential.
- The voltage across a cell’s membrane
- resting = -70mV as fluid is more negatively charged inside the cell.
leakage channels vs. voltage-gated channels
- leakage - always open.
- voltage-gated - require activation of action potential to open (usually by sodium pump).
What is the sodium potassium pump?
- three sodium (from intracellular fluid) and one ATP are used to push K+ into the membrane by fusing with a carrier protein (SPP).
- since the channel is altered, two K+ ions can enter.
- creates a net reduction of positive ions and is a process of active transport.
Discuss depolarisation.
- a sudden increase in membrane potential - occurs if 15mV is exceeded.
- begins by sodium channels being opened on synpatic knobs.
- Sa+ enter intracellular fluid, making inside more positive and outside more negative.
- -55mV needs to be reached to open voltage-gated channels, subsequently allowing more and more sodium ions to flow in.
ligand-gated channels vs. mechanical-gated channels
- ligand-gated - open when a neurotransmitter latches onto the protein.
- mechanical-gated - open due to physical stretching of the membrane.
Describe the formation and composition of CSF
- clear and watery substance
- produced in ventricles and held in meninges and ventricles.
- main function is to protect, support, nourish, and transport substances in the CNS.
- delivers nutrients and removes wastes and toxins from CNS.
- Contains: Glucose, urea, proteins, and salts.
- Shock absorbing medium.
What does the cerebrum do?
contains the 4(5) main sects of the brain with the three main functional areas - sensory, motor, and association.
- Frontal Lobe: voluntary muscle control, judgement, emotions, memory.
- Temporal lobe: olfactory and auditory areas, linking memories and senses together.
- Occipital lobe: solely visual reception
- Parietal lobe: temperature, touch, pain, taste, and movement.
- Insula: autonomic NS control, senses, and emotions.
What does the cerebellum do?
- Receives info from inner ear receptors to coordinate parasympathetic balance.
- Receives info from skeletal muscles to coordinate muscular movement regarding the lengths of muscles.
What are the roles of the hypothalamus?
Regulates:
- autonomic NS (heart rate, blood pressure, digestive actions etc.);
- body temperature;
- food/water intake;
- waking and sleeping cycles;
- emotions; and
- hormonal secretions.
What does the medulla oblongata do?
automatically adjusts all body functions and houses three main centres:
- respiratory centres - control breathing actions and lung movement (depth and rate);
- cardiac centre - regulates rate and strength of heartbeat.
- vasomotor centre - controls diameter of blood vessels.
Describe the three meninges to me.
The meninges are connective tissue membranes that serve to protect, nourish, and support the CNS.
- dura mater (outer layer) - tough and fibrous, main function is to support and protect.
- arachnoid mater (middle layer) - full of CSF to absorb shock from impact.
- pia mater (inner layer) - thin, yet heavily vascularised and carries food and o2 to cells.
Label and discuss this diagram of the spinal cord.
What are its functions?
How is it structured to fufill this (kept in white matter)?
Functions: to communicate with the brain by sending electrical impulses and to act on reflexes.
Ascending tracts have sensory axons that travel upwards.
Descending tracts have motor axons that travel downwards.
What does the corpus callosum do?
What does the pons do?
CC: a wide band of connective fibres that holds the two cerebral hemispheres together.
Pons: relays information from the medulla oblongata to higher centres i.e. the hypothalamus.
What are totipotent cells?
- they have an unlimited capacity to differentiate.
- taken from a 1-5 day old embryo.
What are pluripotent cells?
- have the capacity to differentiate into a majority of somatic cells.
- taken from the inner cell mass of the blastocyst at around 5-14 days old.
What are multipotent cells?
- have the capacity to differentiate into a limited number of somatic cells.
- can be taken from the foetal tissue, umbilical cord, and most adult somatic cells.
Describe Alzheimer’s disease
- Causes: Atrophy of the brain, brain cells die in lobes, tau tangles and amyloid plaques tangle around neurons, myelin sheath breaks down, acetylcholine inhibited.
- Symptoms: Dementia, lack of memory, coordination limited, independence stripped.
- LTEs: Death, lack of social skills, reliance on others, smaller brain.
Describe Parkinson’s disease
- Causes: Neurons don’t produce enough dopamine, thus limiting the conduction of nerve impulses across a synapse.
- Symptoms: Tremors, bradykinesia, rigidity, postural instability, speech changes, writing changes.
- LTEs: Loss of executive functioning, thinking, memory, showing emotion, decision making and coordination.
