Nervous System Flashcards
What are the key roles? Neurones play?
They form connections between different groups of cells in order to:
Gather the information from sensory receptors
Process information and create memory in the central nervous system
Stimulate affector cells in voluntary movement or gland secretions
What five types of cells is the nervous system composed of?
Neuron
Glial cells
Microglial cells
Connective tissue
Blood vessels
Explain afferent neurons and efferent neurons
An afferent neuron or a sensory neuron describes a neuron that transmits nerve impulses from sensory cells towards the spinal cord
An efferent neuron refers to a motor neuron that transmit signals from the brain and spinal cord towards the muscles and glanular organs
If a nerve impulse is headed from the brain to the muscle muscles and glandular organs, what type of neuron is this?
An efferent neurone or motor neurone
Describing explain the components of a neuron
Cell body – this contains the nucleus and normal organelles such as many mitochondria needed to maintain readiness for action potential
Axons – these are fibres that conduct electrical impulses away from the cell body Each neuron only has a single axon.
Dendrites– connecting fibres/branches of which each neuron has thousands of hair like projections which enable communication between neurons
Myelinated sheath – an insulating sheath around the axon which increases the speed of which an impulse is conducted
Nodes of ranvier – interruptions 1 mm in the myelinated sheet that causes the changing potential to jump from one load to another shortening the speed of conduction
Synapse a small gap in between neurons sometimes dendrites and cell bodies filled with interstitial fluid which requires chemical communication as nerve impulses cannot jump the gap
Synaptic knob – the terminal the end of the neuron responsible for chemical communication
What is a synapse?
A very small gap between neurons often between two dendrites or dendrite and a cell membrane or so body the gap is filled with interstitial fluid however the neurons do not touch due to this the nerve impulse cannot jump over the gap and communication is instead chemical
The time taken to cross a synapse is 0.5 seconds
Explain a synaptic knob
Be terminal end of neuron it contains chemical neurotransmitters such as dopamine serotonin, adrenaline. The communication between neurons are facilitated by the synaptic knob through these neurotransmitters diffusing across the gap stimulating postsynaptic membrane receptors call it an effect on the post synaptic cell.
Explain glial cells
Another type of nervous tissue is a neuroglial cell which carry out support functions e.g. in case of injury these cells Multiplan fill the spaces formally occupied by neurons. However these cells are genuinely smaller than neurons and 50 times more numerous.
Some of these cells have immune system function. primary brain tumours. Mostly derived from the cells.
Explain the concept of resting potential
Resting potential is when a inactive neuron is more negative on the inside than the outside or polarised
The polarised membrane as a potential difference of -70Mv
Explain the concept of action potential
Action potential describes a positive difference open (40mV) across the axon membrane caused by a neurotransmitter or stimuli.
The stimuli causes a change in the permeability of the axon membrane to sodium ions , specific sodium ion channels open and sodium ions diffuse rapidly into the axon down the concentration and electrochemical gradient resulting in a brief reversal of potential across the axon membrane from polarise to depolarised.
Action potential lasts one ms and it isn’t all oh nothing response it happens or it doesn’t
Explain the concept of a refractory period
A refractory period refers to the period after an action potential where the area of the axon cannot be stimulated again and is a period of reparation
The sodium ion channels close and sodium/potassium pump quickly pumps out the excess sodium ions this is an active process requiring ATP the permeability to the membrane to potassium briefly increases so potassium ions diffuse out of the axon down both concentration and electrochemical gradient
The potential across the axon membrane is eventually raised back to resting potential. This delay limits the amount of impulses that control across a neuron and stops neuron travelling in multiple directions.
Explain a action potential spreading to a axon membrane step-by-step
Step-by-Step Spread of an Action Potential Along the Axon
1. Resting State (-70 mV)
• The neuron is at rest, with Na⁺ (sodium) outside and K⁺ (potassium) inside the axon.
• Voltage-gated Na⁺ and K⁺ channels are closed.
2. Depolarization (Threshold ~-55 mV to Peak ~+30 mV)
• A stimulus causes Na⁺ channels to open at the axon hillock, allowing Na⁺ to rush in.
• If threshold (~-55 mV) is reached, more Na⁺ channels open, and the membrane rapidly depolarizes to around +30 to +40 mV.
3. Propagation (Wave of Depolarization Moving Along the Axon)
• The local positive charge spreads, causing nearby Na⁺ channels to open, continuing depolarization along the axon.
• The previous segment starts repolarizing while the next segment depolarizes, ensuring one-way conduction.
4. Repolarization (+30 mV to ~-70 mV)
• Na⁺ channels inactivate, stopping further Na⁺ entry.
• K⁺ channels open, allowing K⁺ to exit, restoring negativity inside the membrane.
5. Hyperpolarization (~-80 to -90 mV, then back to -70 mV)
• K⁺ channels stay open too long, making the membrane temporarily more negative than resting potential.
• Na⁺/K⁺ pump restores the original ion balance, bringing the neuron back to -70 mV.
6. Refractory Period (Prevents Backward Movement)
• Absolute Refractory Period: No new action potential can fire (~peak to mid-repolarization).
• Relative Refractory Period: A stronger stimulus is needed (~hyperpolarization phase).
This cycle repeats at each section of the axon until the signal reaches the synaptic terminals.
Explain the process of an action potential crossing a synapse
How Signals Cross the Synaptic Gap (Synaptic Transmission)
1. Action Potential Arrives at Axon Terminal
• The electrical impulse reaches the presynaptic neuron’s axon terminal.
- Voltage-Gated Ca²⁺ Channels Open
• The depolarization from the action potential causes voltage-gated Ca²⁺ channels to open.
• Ca²⁺ ions rush into the presynaptic neuron. - Neurotransmitter Release
• The influx of Ca²⁺ triggers synaptic vesicles (tiny sacs) to move toward the membrane.
• Vesicles fuse with the membrane and release neurotransmitters into the synaptic cleft (gap). - Neurotransmitter Binds to Receptors on Postsynaptic Neuron
• Neurotransmitters diffuse across the synaptic gap and bind to specific receptors on the postsynaptic membrane.
• The type of receptor determines the response:
• Ionotropic receptors (ligand-gated ion channels) open immediately.
• Metabotropic receptors (G-protein-coupled receptors) trigger slower, longer-lasting effects. - Ion Channels Open (Excitatory or Inhibitory Response)
• If the neurotransmitter is excitatory (e.g., glutamate, acetylcholine):
• Na⁺ channels open, Na⁺ rushes in → depolarization → action potential more likely.
• If the neurotransmitter is inhibitory (e.g., GABA, glycine):
• Cl⁻ channels open (Cl⁻ enters) or K⁺ channels open (K⁺ leaves) → hyperpolarization → action potential less likely. - Signal Ends (Neurotransmitter Removal)
• The neurotransmitter is removed from the synapse in three ways:
• Reuptake (taken back into the presynaptic neuron, e.g., serotonin via SERT transporter).
• Enzymatic breakdown (e.g., acetylcholine broken down by acetylcholinesterase).
• Diffusion (neurotransmitter drifts away). - Postsynaptic Neuron Fires or Remains Inactive
• If the sum of excitatory and inhibitory inputs reaches the threshold, a new action potential starts in the postsynaptic neuron.
• If not, the signal stops there.
This process repeats at every synapse until the message reaches the final target, like a muscle or brain area.
Explain how a resting potential is maintained and what this has to do with sodium and potassium
How Resting Potential is Maintained
1. Resting Potential (-70mV)
• Inside of neuron is more negative than outside.
• Maintained by Na⁺/K⁺ pump and leaky K⁺ channels.
- Sodium-Potassium Pump (Active Transport, Uses ATP)
• Moves 3 Na⁺ out and 2 K⁺ in.
• Keeps more Na⁺ outside and more K⁺ inside. - Leaky K⁺ Channels (Passive Diffusion)
• Always open, letting K⁺ leak out, making inside more negative.
• Na⁺ channels mostly closed, stopping Na⁺ from leaking in. - Electrochemical Gradient & Balance
• K⁺ wants to leave due to concentration gradient.
• Negative charge inside pulls K⁺ back (electrical gradient).
• Balance creates resting potential (~ -70mV). - Why It Matters
• Keeps neuron ready to fire when stimulated.
• Disruption (e.g., no ATP) = neuron can’t function.
• Action potential starts when voltage-gated Na⁺ channels open.
Describe the difference between exteroreceptors and interoreceptors
exteroreceptors receive external stimuli from outside the body such as light, sound and smell smells
interoreceptors receive internal stimuli such as water levels in the body (first) and nutrient levels (hunger) and carbon dioxide concentration in the blood and blood pressure
Explain the concept of adaptation when it comes to receptor. Give examples of slow and fast adapting sensors.
Adaptation is the concept that in the presence of constant stimulus neurons eventually stop responding and sensitivity is greatly reduced seen when we tune out repetitive low-level noise or chronic pain
A fast adapting sensor would be a thermal receptor as when you enter a cold room your body adjust
Slow adapting receptors would be nociceptor which detect pain
What are nociceptors and where are they located?
They detect pain and are slow adapting receptors, especially common in the skin joint capsules, bone, and around the walls of blood vessels
Deep tissue and visceral organs have few nociceptors
What are thermal receptors and where are they found?
Thermal receptors are fast adapting found in skin skeletal muscles, liver, and the hypothalamus
Cold receptors are 3 to 4 times more abundant than heat receptors
Explain mechanoreceptors and how they are both interceptor and exteroreceptor
Mecano receptors can be split into three groups
baroreceptor – detect pressure changes in walls of blood vessels (interceptor function)
Proprioceptors – monitor the position of joints and muscles (most structurally complex interceptor)
Tactile receptors – provide sensations of touch pressure of vibration H and tickle ( exteroreceptor function
Explain chemoreceptors
Chemical receptors of both exteroreceptor and interoreceptor as the detective chemical changes in the mouth and nose as well as within chemicals and body fluids
Explain Osmoreceptors
Osmoreceptors interceptors that detect changes in water potential of body fluids
Explain photos receptors
Detector light
What does the central nervous system consist of?
The brain and the spinal cord
Describe the structure of the brain protective layers as well as the rule that cerebrospinal fluid plays
The brain located in the skull cavity has 1.5 kg weight and over 12 billion neurons and 50 billion supporting glial cells
The brain is also protected by three membranes
Dura Mater – a tough leather remembering that forms an inelastic bag that surrounds the brain and spinal cord
Archnoid mater – a spiderweb like middle layer
Pia mater – a thin membrane that adhere closely to the surface of the brain
Between the archanoid mater the pia Mater is a sub arachnoid space which contains cerebrospinal fluid which AIDS in transport of nutrients to the CNS and removal of waste as well as a physical shock barrier
Explain the medulla oblongata’s location and function
Medulla Oblongata
• Location:
• The medulla oblongata is the lowest part of the brainstem, connecting the spinal cord to the brain.
• It sits just below the pons and above the spinal cord, passing through the foramen magnum of the skull.
• Functions:
1. Autonomic Control: Regulates vital involuntary functions, including:
• Heart rate (via the cardiac center)
• Blood pressure (via the vasomotor center)
• Breathing rate & rhythm (via the respiratory center)
2. Reflexes: Controls protective reflexes such as:
• Coughing, sneezing, swallowing, and vomiting
3. Motor & Sensory Pathways:
• Contains ascending (sensory) and descending (motor) tracts that pass between the brain and spinal cord.
• Houses the pyramidal decussation, where motor signals cross, meaning the left brain controls the right body and vice versa.
Explain the location and function of the pons
Pons
• Location:
• The pons is part of the brainstem, sitting above the medulla oblongata and below the midbrain.
• It lies in front of the cerebellum and connects the brainstem to the higher brain regions.
• Functions:
1. Bridge for Communication:
• Relays signals between the cerebrum, cerebellum, and spinal cord.
2. Respiratory Control:
• Works with the medulla oblongata to regulate breathing rhythms (via the pneumotaxic and apneustic centers).
3. Motor Control & Coordination:
• Helps control facial expressions, chewing, and eye movements.
4. Sensory Functions:
• Involved in hearing, balance, and touch sensations from the face.
5. Sleep & Arousal:
• Plays a role in sleep regulation and alertness (via the reticular formation).
Which part of the brain has a signature ridged appearance and controls muscular activity muscle tone resistance to stretch and motor coordination such as balance and posture
Cerebellum
• Location:
• The cerebellum is located at the back of the brain, below the occipital lobe and behind the brainstem (pons and medulla oblongata).
• It is separated from the cerebrum by the tentorium cerebelli and connected to the brainstem via the cerebellar peduncles.
• Functions:
1. Motor Coordination:
• Ensures smooth, precise, and coordinated movements.
2. Balance & Posture:
• Maintains equilibrium by integrating signals from the inner ear, muscles, and eyes.
3. Muscle Tone Regulation:
• Adjusts muscle tension for controlled movements.
4. Motor Learning:
• Helps with learning new movements (e.g., riding a bike, playing an instrument).
5. Cognitive Functions (Minor Role):
• Involved in some attention, language, and problem-solving tasks.
Although the cerebellum doesn’t initiate movement, it fine-tunes and corrects errors for smooth motor execution.
Explain the midbrain and its location and function
The mid range is located above the ponds and is the narrow part of the brain stem
It controls visual and auditory functions such as site and hearing
What is the cerebral cortex and give it locational context as well as functional context?
The outer layer of the cerebrum which is the largest part of the brain, it can be divided into lobes which would be the frontal lobe and the temporal lobe which have more specialised functions
The cerebrum is the centre of intelligence, personality judgement, decision-making, consciousness, and memory
Explain the thalamus its location and function
This is a relay station which linked areas of the cerebral cortex involved in sensory perception and movement with other parts of spine and brain
It organise the sensory information and distribute as appropriate in addition to being involved in the control of sleep and wakefulness
Which part of the brain deals with coordinating hormonal and nervous functions concerned with homeostasis such as the control of water balance and regulating temperature and the release of hormones involved in the control of metabolism and reproduction?
The hypothalamus is in charge of coordinating hormonal and nervous functions concerned with homeostasis
Explain cranial nerves
Brain has 12 pairs of cranial nerves some contain only motor fibre some contains sensory neurons and other container mixture of both
Olfactory Nerve (I)
• Function: Smell (sensory)
2. Optic Nerve (II)
• Function: Vision (sensory)
3. Oculomotor Nerve (III)
• Function: Eye movement (motor), pupil constriction (autonomic)
4. Trochlear Nerve (IV)
• Function: Eye movement (motor)
5. Trigeminal Nerve (V)
• Function: Sensory to face (sensory), chewing (motor)
6. Abducens Nerve (VI)
• Function: Eye movement (motor)
7. Facial Nerve (VII)
• Function: Facial expression (motor), taste (sensory), salivation (autonomic)
8. Vestibulocochlear Nerve (VIII)
• Function: Hearing and balance (sensory)
9. Glossopharyngeal Nerve (IX)
• Function: Taste (sensory), swallowing (motor), salivation (autonomic)
10. Vagus Nerve (X)
• Function: Heart rate, digestion, speech (autonomic & motor), taste (sensory)
11. Accessory Nerve (XI)
• Function: Shoulder movement, head turning (motor)
12. Hypoglossal Nerve (XII)
• Function: Tongue movement (motor)
What is the key difference between grey matter and white matter?
White matter is found in the central area of the spinal cord as well as the cerebral cortex
Grey matter is made of axon synapses cell bodies and dendrites and does not have myelinated sheets
Grey matter functions by processing and sorting information whereas white matter transmits signals between parts of the brain and spinal cord
Explain the structure of the spinal cord
31 pairs of spinal nerves stem from the spinal cord each with motor and sensory components
Cross-section near the spinal cord appears an oval plate with a H or butterfly in the middle which is grey matter which consists of nerve cells and cell bodies
The remaining area is white matter which consist of nerve fibres and have myelinated sheets, unlike the grey matter
Where bundles of nerves exist in the spinal cord these are called nerve trucks whether there is a collection of nerve cell bodies this is called a ganglion
What is a ganglion?
A ganglion is a bundle of nerve cell bodies
Explain the function of the blood brain barrier and how it works
Blood-Brain Barrier (BBB) – Flashcard Format
- Function of the BBB
• Protects the brain by controlling what enters from the blood.
• Prevents toxins, pathogens, and excess ions from disrupting brain function.
• Regulates nutrients (e.g., glucose, amino acids) and maintains a stable environment for neurons. - How the BBB Works
• Tight Junctions: Endothelial cells are tightly sealed, stopping most substances from leaking in.
• Astrocytes: Support cells that help regulate transport.
• Selective Transport Proteins: Allow necessary molecules (e.g., glucose, amino acids) to cross.
• Lipid-Soluble Molecules: (e.g., oxygen, CO₂, alcohol, nicotine) can diffuse through. - What Can & Can’t Cross
✅ Can Cross:
• Oxygen & Carbon Dioxide (passively diffuse).
• Glucose & Amino Acids (via transporters).
• Small, fat-soluble molecules (e.g., alcohol, caffeine, nicotine).
❌ Can’t Cross Easily:
• Large molecules (e.g., proteins, most drugs).
• Charged molecules (e.g., many toxins).
• Most bacteria & viruses (except some like meningitis-causing bacteria).
- Weak Points in the BBB
• The hypothalamus has a weaker barrier to allow hormones to enter the bloodstream for body regulation.
• The circumventricular organs (CVOs), like the area postrema (vomiting center), lack a strong BBB to detect toxins in the blood.
• These weak points can be exploited by drugs, allowing some substances to bypass the barrier. - Why It Matters
• Protects the brain from infections and toxins.
• Ensures neurons function properly by preventing chemical imbalances.
• Makes treating brain diseases difficult since many drugs can’t cross the BBB.
What is the peripheral nervous system and what can it be split into?
The peripheral nervous system consist of all the nerve tissue that does not belong to the CNS and it is divided into voluntary (somatic) nervous system or involuntary (autonomic) nervous system
Explain the somatic nervous system and how it governs control in addition to where its neurons are located
The somatic nervous system is concerned with all activities under conscious control and the majority of its receptors are mechanoreceptors
Although some involuntary reactions such as breathing or controlled by somatic neuron activity as the muscles that generate the respiration movement skeletal
Somatic motor pathways always involve at least two motor neurons and upper motor neuron who sell body is contained within a CNS processing centre under the lower neuron who cell body is contained in a nucleus of the brain stem or spinal cord
Destruction of the lower motor neuron will cause loss of voluntary and reflect control over the motor unit (muscle) and paralysis
Explain autonomic nervous system
The autonomic nervous system is divided anatomically into two distinct opposite pathways
Sympathetic, which is largely excitatory and is related to increased heart rate and rising blood pressure (fight or flight)
Parasympathetic largely inhibitory tends to slow down hot and breathing and it’s composed of many branches of the vagus nerve
Most autonomic neurons are interceptors And although it is hard to consciously control the autonomic system, it isn’t impossible such as strong emotions causing angina pectoris as the autonomic nervous system receives a message through the autonomic sensory neurons
Where are nociceptors seen most?
Nice receptors are especially common just under the skin in joint capsules and within periosteum membrane surrounding bones
Explain fast pain versus slow pain
Fast Pain vs. Slow Pain – Flashcard Format
- Fast Pain (Sharp, Immediate Pain)
• Detected by: Aδ (A-delta) fibers – small, myelinated fibers that conduct signals fast (5-30 m/s).
• Type of Pain: Sharp, localized, stabbing pain (e.g., cutting or burning skin).
• Neurotransmitter Used: Glutamate – quickly excites neurons in the spinal cord to send pain signals to the brain.
• Pathway: Travels via the neospinothalamic tract to the somatosensory cortex for precise localization. - Slow Pain (Dull, Aching Pain)
• Detected by: C fibers – unmyelinated fibers, conducting signals slowly (0.5-2 m/s).
• Type of Pain: Dull, burning, throbbing pain (e.g., deep tissue damage, inflammation).
• Neurotransmitters Used:
• Glutamate (initial quick signal).
• Substance P (sustains pain, making it more intense and harder to ignore).
• Pathway: Travels via the paleospinothalamic tract to the limbic system, affecting e
Explain how the feeling of pain travels from the sensory neuron to affect the brain and how the brain processes it
- Pain detected by nociceptors.
- Signal sent via sensory neurons to the spinal cord. Afferent
- Spinal cord relays it to the thalamus in the brain.
- Brain processes pain (location, intensity, emotion, and reaction).
- Pain modulation occurs through descending pathways (endorphins help suppress pain).
This system ensures pain is felt, processed, remembered, and controlled for survival and adaptation.
What is the role of endorphins and enkephalins in controlling pain
The level of pain felt can be reduced with the release of peptides such as endorphins within the CNS
the peptides are neuromodulators as they sometimes don’t act as neurotransmitters but instead increase or decrease the action of neurotransmitters
Impulses from the brain or passed down the spinal ganglia where they can modulate the incoming pain pathways
Explain the gate control theory of pain
The gate control theory of pain states that normal pain is self limiting. The pain is quickly suppressed by the brain sending nerve pathways in the spinal cord while ache of C fibres resolves more slowly
Nerve impulses generated by the brain close the gate stopping pain transmission failure to control. These mechanisms can lead to chronic pain which persists after removal of the cause or affect.
Explain sense organs how they work and the five main sensory systems in the body
Sensory receptors are often found together with sense organ since organ respond to changes in the environment and impulses that travel along the sensory neurons to the CNS
Five sensory systems
Sight – the eyes
Sound and balance – the ears
Touch, temperature, pain and body position – sensory receptors in the joint skin muscles and semi circular canals the ears
Taste – the tongue closely linked to sense of smell
Smell – the nose
What does the lachrymal glands produce?
Tears which serve to lubricate the eye as well as contain Auntie antibacterial enzyme lysozyme
How does light travel into the eye to the brain to be interpreted give a step-by-step?
Pathway of Light from the Eye to the Brain
- Light Enters the Eye
• Cornea: The first structure light passes through; bends (refracts) light to focus it.
• Aqueous Humor: Fluid-filled chamber that helps maintain eye pressure and further refracts light.
• Pupil: The opening in the iris that controls how much light enters.
• Lens: Fine-tunes focus by changing shape (accommodation) via the ciliary muscles.
• Vitreous Humor: A clear, gel-like substance that maintains the eye’s shape and helps direct light onto the retina. - Light Reaches the Retina (Phototransduction Occurs)
• Retina: The light-sensitive layer at the back of the eye.
• Photoreceptors (Rods & Cones):
• Rods: Detect dim light (black & white vision, night vision).
• Cones: Detect color (red, green, blue) and work best in bright light.
• Phototransduction: Light is converted into electrical signals by breaking down rhodopsin (in rods) and photopsin (in cones). - Signal Travels Through the Retina’s Neural Layers
• Bipolar Cells: Relay signals from photoreceptors to ganglion cells.
• Ganglion Cells: Their axons form the optic nerve and send visual information to the brain. - Signal Travels to the Brain via the Optic Nerve (CN II)
• Optic Nerve (CN II): Carries visual signals from each eye to the brain.
• Optic Chiasm: The point where some nerve fibers cross so that the left visual field goes to the right brain and vice versa.
• Optic Tracts: Carry visual information to the thalamus. - Signal Reaches the Brain for Processing
• Lateral Geniculate Nucleus (LGN) of the Thalamus: First major processing center; organizes and relays visual information.
• Primary Visual Cortex (Occipital Lobe, V1): Processes basic shapes, edges, and movement.
• Higher Visual Areas (V2-V5 & Association Areas): Interpret color, depth, and object recognition. - Final Interpretation
• The brain fully interprets the image, combining signals from both eyes for depth perception and recognizing objects.
What is the sclera?
The outer coat of the eye (white of the eye)
Protects sensitive underlying structures and preserve shape of eyeball optic muscles are attached to sclera
What is the cornea?
At the front of the eye, the sclera converts into a transparent tissue called the cornea which bends and reflects light coming into the eye towards the retina
What is the choroid?
The middle part of the eye containing blood vessels
What is aqueous humour?
This fills the front chamber of the eye and helps reflect incoming light rays
What is vitreous humour?
A transparent jelly which fills the whole of the back of the chamber of the eye
What is the lens in reference to the eye?
This changes shape to focus light onto the retina find focusing that enables us to see clearly it is short and flat to focus light from close objects and long and thin to focus light from distant objects
What is the pupil?
The hole in the middle of the iris which changes diameter to control the amount of light entering the eye
In bright light, the muscles in the Irish shrink the pupil to limit the amount of light entering the eye and vice versa
What is the iris’s role?
A pigmented muscular die from which controls the amount of light entering the eye by changing the diameter of the pupil
What is the function of the retina?
Contains light sensitive cells, rods, and cones
Each retina contains 120 million rods and 6 million cones
Roads remain sensitive at low light levels and are more numerous at the edge of the runner. Cones are only simulated by bright light. There are more numerous in the centre of the rest.
Describe the outer ear
Outer Ear (External Ear)
The outer ear is the first part of the auditory system, responsible for collecting and directing sound waves toward the inner structures of the ear.
Main Parts of the Outer Ear:
1. Pinna (Auricle)
• The visible part of the ear.
• Made of cartilage and skin.
• Funnels sound waves into the ear canal.
- External Auditory Canal (Ear Canal)
• A tube-like passage that carries sound toward the eardrum.
• Lined with hair and ceruminous glands, which produce earwax (cerumen) to trap dust and debris. - Tympanic Membrane (Eardrum)
• A thin, flexible membrane that vibrates when sound waves hit it.
• Transfers vibrations to the middle ear bones (ossicles).
Describe the middle ear
The cavity between the eardrum and the inner ear contains the ear ossicles the three smallest spoons in the body. The eardrum receives vibrations travelling up the canal and transfer them onto the ossicles which transferred to the inner ear
The malleus – hammer
Incus – anvil
Stapes– stirrup
The eardrum is 15 times larger than the oval window which amplifies these vibrations
Describe the inner ear
The inner ear is the most complex part of the ear, responsible for converting sound vibrations into electrical signals that the brain can interpret, as well as helping to maintain balance.
Bony Chambers of the Inner Ear:
1. Cochlear Chamber
• Located in the cochlea, this chamber is responsible for hearing. It contains the fluid-filled canals that house the hair cells responsible for converting sound vibrations into electrical signals.
2. Vestibular Chamber
• This chamber contains the vestibule and the semicircular canals, which are responsible for balance and detecting motion. These structures detect head movements and send signals to the brain to help maintain equilibrium.
Explain the two organs in the inner ear and their roles
Inner Ear Organs & Their Roles
- Cochlea (Hearing Organ)
• Function: Converts sound vibrations into electrical signals for the brain.
• Structure:
• Basilar Membrane: Detects different sound frequencies.
• Organ of Corti: Contains hair cells (mechanoreceptors) that detect sound waves.
• Tectorial Membrane: Bends hair cells, triggering nerve impulses.
• Process:
• Sound waves travel through the cochlear fluid.
• Hair cells bend, causing depolarization and releasing glutamate.
• The auditory nerve (CN VIII) sends signals to the brain for interpretation. - Vestibular System (Balance & Spatial Orientation)
• Function: Detects head position, movement, and balance.
• Main Structures:
• Semicircular Canals: Detect rotational movements.
• Otolith Organs (Utricle & Saccule): Detect linear acceleration & gravity.
• Process:
• Movement causes fluid (endolymph) in the semicircular canals to shift.
• Hair cells in the ampulla & otolith organs detect this movement.
• Signals travel via the vestibular nerve (CN VIII) to the brainstem & cerebellum to maintain balance.
Why This Matters
• Damage to the cochlea → hearing loss.
• Damage to the vestibular system → dizziness & balance issues (vertigo).
Explain the olfactory pathway to the brain
Olfactory receptor cells have a large central bulge containing the nucleus and two further cytoplasmic extensions one of which extends the surface of the epithelium of the nose to detect smells on the other penetrates the basement membrane and impulses to the brain
Olfactory mucosa which census smell and also some aspects of taste is located on the roof of the nose in an area. A sizeable postage stamp has around 10 to 100,000,000 receptors for smell.
Olfactory transduction site is the olfactory hairs which are cellular that project from cell dendrites
Areas involved in interpretation of smell include the limbic system (emotional response) and the hypothalamus (autonomic response)
What are the anatomical and physiological changes in the nervous system that begin around the ages of 30?
And what is the impact?
A reduction in brain size and weight primarily due to a decrease in the size of the cerebral cortex
A reduction in the number of cortical neurons
A decrease in blood flow to the brain caused by fatty deposits in blood cells
Changes in synaptic organisation of the brain in many areas the number of dendrite branches and into connections appear to decrease
These changes contribute to dementia Alzheimer’s and Parkinson’s around 20% of the elderly population. You are affected by these changes whereas 80% of the population. These changes are not significant.
Explain cerebrovascular accident
This is the name given to an illness which part of the brain is damaged or destroyed due to a clot or haemorrhage which affects blood supply to that area of the brain
This result in a lot of function of those parts of the brain and can lead to speech visual and facial contortion problems usually on one side of the body
Symptoms reduce as brain reduces damage can be so sense of the patient dies
Explain multiple sclerosis
Multiple sclerosis is an autoimmune disease that attacks the myelinated sheet of neurons partially or completely stripping them leaving lesions or plaques
Loss of the myelinated sheet disrupts no impulses slowing distorting or making them pass from one nerve to another called short circuit
It’s kind of also damaged the nerve itself causing onset of disability that can progress overtime
Explain dementia
Dementia is a term used to describe various brain disorders that feature a loss of brain function usually progressive and eventually severe their over 100 types of dementia
Alzheimer’s disease of vascular dementia and dementia with LEWY bodies or some of the common ones and the symptoms include:
Loss of memory confusion, speech and understanding problems and loss of ability to carry out normal functions in everyday life
Explain epilepsy
Epilepsy is the tendency to have recurrence seizures which are caused by a sudden burst of electro activity in the brain causing temporary disruption to normal impulses passing between brain cells
There are multiple types of seizures, however a person suffering may not be able to control their movements have unusual sensation or feelings also suffer for a loss of consciousness
The majority of epilepsy around 60% has no known cause and is this idiopathic epilepsy
Describe the difference between psychosis and neurosis
Psychosis is a severe Servant in psychology of a patient who uses touch with reality
Neurosis is why a patient is still suffering exaggerated behaviour but is aware of their clinical condition
Explain effective mood disorders
Affected mood disorders or emotional disturbances consisting of prolonged periods of excessive sadness the slow mood lack of enjoyment or pleasure or excessive joyousness or both
Mood disorders can be unipolar just depressive or bipolar both
Explaining schizophrenia
Schizophrenia is when someone cannot tell the difference between real and imaginary and is described as a psychotic illness. It can arrange from person to person and can be either a long-term illness or a short term which has only one psychotic event.
Symptoms can be described as:
Positive – hallucinations and delusions commonly hearing voices
Negative – withdrawal lack of communication drive or detachment from people places family and job
Cognitive – difficulty understanding information using it to make decisions trouble focusing or paying attention and problems with working memory
Explain personality disorders
Personality disorders cause a person to think feel or behave different to most other people leading to difficulties maintaining friendships and relationships
The main categories are suspicious, emotional, impulsive, and anxious
Describe the three main disorders of the eye
Cataracts
Glaucoma
Mucular degradation
Cataracts forms when the normal transparent lens becomes progressively more opaque and cloudy as protein deposits up causing gradual loss of site
Glaucoma is due to the normal pressure with in the eye (15 to20 MMHG) increases usually caused by an obstruction in the anterior chamber which contains the aqueous humour which can reduce or blocked the blood flow to the retina ultimately resulting in blind
Macular degradation is common in older people and it is when the central part of the retina the macula stops working side vision is not lost but people affected can no longer focus clearly on what is directly ahead of them
What is otitis?
Otitis is usually classified as otitis externa or media and refers to inflammation of the external canal or middle ear due to allergy bacteria, fungi viruses, or trauma
Describe the three main nose disorders
Sinusitis
Anosmia
Nasal polyps
Sinusitis – Inflammation of the Musa membrane lining the airfield sinuses it causes pressure, pain, headache, fever, and local tender
Anosmia – loss of sense of smell resulting from head injuries or after the effects of nasal inflammation can also be caused by aging or smoking or psychological factors such as phobia or fear associated with certain smells in a third of the cases is caused by a zinc deficiency and it’s easily corrected once zinc supplements prescribed
Nasal polyps – these result from either chronic infection, inflammation or chronic allergic information. They consist of rounded elongated pieces of pulpy connective tissue infiltrated with chronic inflammatory cells that project into the nasal cavity.
Explain a ACHE inhibitors
ACHE inhibitors are used to improve some of the symptoms of early Alzheimer’s disease and slow down the progression of the illness as there is no cure
Alternatively, medicines aimed at Parkinson’s disease occur because the dopamine in the brain has become too low medicines aim to increase the level of dopamine preventing its destruction and stimulate the parts where dopamine acts
Describe the efficacy of epilepsy treatment and the aim
Epilepsy treatment aims to stabilise the electrical activity in the brain and prevent seizures occurring
8 out of 10 patients medication is very effective
Explain the action of hypnotics
Hypnotic aim to promote sleep and include a benzodiazepines
Anxiolytics open (sedatives) induce sleep when given at night
Tolerance can be developed if physical and psychological dependence occurs
What is used to treat patients who are suffering from schizophrenia, bipolar disorder, severe anxiety or depression?
Antipsychotics are used to treat the following disorders and they affect neurotransmitters in the brain, especially dopamine
Explain antidepressants giving the most commonly prescribed ones
Serotonin reuptake inhibitors SSRI are the most commonly prescribed and they aim to increase the sign up concentration of the neurotransmitter serotonin and no adrenaline in the brain
They tend to be effective in the treatment of moderate and major depression less so in lower grade chronic depression
What type of medicine would be recommended to treat glaucoma?
Miotics are used to treat a coma they help improve the drainage of the aqueous humour lowering the pressure inside the eye reducing risk of long-term damage and blindness
What would be used to treat otitis and sinusitis
Antibiotics can be used to treat any bacterial infection of the nervous system, including otitis media and sinusitis
