Lecture notes
Nerves & Muscles (IMS)
- Institution
- University Of Leeds (UoL)
Introduction to Medical Sciences TOPIC 12 - Nerves & Muscles
[Show more]
Content preview
Medic_Summaries (IMS) Topic 12Muscles and Nerves
CNS: brain and spinal cord (central command centre)
- Receives, processes, interprets and stores information
- Sends messages destined for muscles, glands and organs
PNS: peripheral nerves (body’s link to outside world)
- Transmits information to and from the CNS
- Sensory and motor nerves
ANS: involuntary processes (autonomic)
- Sympathetic, parasympathetic, enteric and cardiac plexuses
- Heart rate, respiration, digestion, pupil contraction etc.
- Operates automatically, without conscious direction
- Sympathetic NS: fight/flight response
- Parasympathetic NS: rest and digestive response
SNS: relays information (somatic)
- Carries sensory information from sensory organs to the CNS
- Relays motor commands to muscles
- Controls voluntary movements
Neurone characteristics:
- Fast communication
- High metabolic rate
- Brain’s grey matter
- Many dendrites - signal input
- One axon - signal conduction
- Many synaptic terminals - signal output
Different types of neurone: size, shape, connections, functions, transmitter
- Sensory
- Motor
- Interneuronal
Multipolar neurones: single long axon, many dendrites emerging from cell body (MOTOR)
Unipolar/ pseudo-unipolar neurones: sensory ganglia (PERIPHERAL SENSORY)
Bipolar neurones: sensory structures (RETINA)
Types of neurite:
- Dendrites: short and thick projections out from the neurone cell body
- Give rise to small spines
- Spread out over a large volume of brain tissue
- Dendritic tissue: increased surface area to receive inputs from other neurones
- Axons: long and thin projections out from the neurone cell body
- Run from one brain area to another/out of CNS to bodily tissues
- Usually only one axon, but may branch off to two/more different targets
Multipolar: pyramidal/stellate
- Cerebral cortex, hippocampus, cerebellum
- Dendrites and axon visual with silver stain
Stellate: small nucleus, many projections (star-like)
Pyramidal: Christmas tree-like
1 Adapted from Lectures at the University of Leeds Medical School
,Medic_Summaries (IMS) Topic 12
White matter: spinal cord consists of axons carrying information to and from the brain
Grey matter: cell bodies in sensory and motor nuclei
Weigert’s strain: stains myelin
- White matter: stains DARK (more myelin as mostly axons)
- Grey matter: stains PALE (less myelin as mostly cell bodies)
The CNS has tracts (axons) and nuclei (cell bodies):
- Group of nerve cells - NUCLEUS
- Bundle of axons - TRACT
The PNS has nerves (axons) and ganglia (cell bodies):
- Group of nerve cells - GANGLION
- Bundle of axons - NERVE
There are four cell groups within the grey matter:
- Somatosensory: SUPERFICIAL dorsal horn
- Viscerosensory: DEEP dorsal horn
- Interneurones respond to inputs from the body’s:
- External tissues (somato) - SOMATOMOTOR: ventral horn
- Internal organs (viscero) - VISCEROMOTOR: intermediate/lateral horn
Tracts: white matter takes information up from the spinal cord to the brain
- Lateral corticospinal tract
- Rubrospinal tract
- Vestibulospinal tract
- Reticulospinal tract
- Ketospinal tract
- Anterior corticospinal tract
The PNS
- Has nerves (axons) and ganglia (cell bodies):
- Dorsal root ganglia: cell bodies of the sensory fibres together with lots of
myelinated and non-myelinated axons passing through
- Ganglia: nodular masses of neurone cell bodies (ganglion cells) and supporting
neuroglia (satellite cells)
- Has two types of ganglia:
- Sensory ganglia: cell bodies of sensory neurones
- Autonomic ganglia: cell bodies of EFFERENT neurones from the ANS
Peripheral nerves:
- Epineurium: covers WHOLE NERVE
- Perineurium: covers FASCICLE
- Endoneurium: covers INDIVIDUAL NERVE AXONS
- NB bindle of nerve fibres = fascicle
Neuroglia/Glia/Glial cells: supporting cells for neurones
- Regulate neurone metabolism and function
- Energy supply and transmitter levels
- Repair and recovery
- Regulate BBB
- Destroy pathogens
- Remove dead neurones
CNS: astrocytes, ependymal cells, oligodendrocytes, microglia
PNS: satellite cells, Schwann cells
2 Adapted from Lectures at the University of Leeds Medical School
, Medic_Summaries (IMS) Topic 12
Astrocytes:
- Extensive projections, spread out between neurones
- Used for contact and communication with neighbouring glial cells and capillaries
- Regulation of ionic concentration: pump ions, such as K+, into capillaries
- Glucose metabolism: take up glucose from blood, convert to lactate and put into
neurones for energy supply
- Neurotransmitter metabolism: take up, inactivate and recycle neurotransmitters and
metabolites
- Regulate BBB: restrict some substances entering brain’s intracellular space
- Neuronal development: produce growth factors to influence neuronal growth and guide
neurones to the correct location and targets
Glial cells:
- In the CNS:
- Astrocytes: involved in metabolic exchange between neurones and blood
- Ependymal cells: lining cells for ventricles/central spinal canal (cilia on lumen)
- Oligodendrocytes: myelinate axons, most common in WHITE MATTER
- Microglia: less common, immune defence (phagocytic)
- In the PNS:
- Satellite cells: surround nerve cell body/aid in controlling chemical environment
of neurones
- Schwann cells: form sheath around large fibres in PNS; phagocytic, engulfs
damaged/dying nerve cells, clears debris allowing regrowth of PNS neurones
Myelination of nerves:
- Oligodendrocytes (CNS)/Schwann cells (PNS) wrap axon in a spiral of concentric layers of
fatty myelinated membranes
- This provides INSULATION and aids in IMPULSE TRANSMISSION
Gaps: 0.5 um between adjacent cells (NODES OF RANVIER)
Sheath: also known as MESAXON, has no cytoplasm and is purely lipid membrane
Nodes of Ranvier: only points along the axon where ions can freely move in and out of the axon,
therefore the action potential ‘jumps’ between nodes (SALTATORY CONDUCTION)
Non-myelinated nerves: supporting Schwann cell
Mesaxon: axon embedded in a channel, Schwann cell is right next to the nerve (single Schwann
cell supports several nerves)
Nerves contain blood: specialised basement membrane to prevent blood leaking into neurone
Osmium: heavy metal, makes myelinated cells stand out under observation
Somatic NS: voluntary NS
- Somatic motor neurones (motoneurones)
- Innervates and controls voluntary, striated (stripped/streaked) muscle
- Has sensory AFFERENT fibres
- Spinal nerves: mixed, consist of EFFERENT motor and AFFERENT sensory fibres
- Motor neurones: one myelinated axon, innervates target organ (e.g. muscle)
- Sensory neurones: special endings, sensory nerve endings
Autonomic NS: involuntary NS
- Controls: heart rate, blood pressure, respiration, sweat glands, gut movements
- Sympathetic and parasympathetic systems (ANTAGONISTIC ACTIONS)
- Unconscious activity: supplies body’s visceral organs
- Sympathetic: SPEEDS UP salivary glands, lungs, heart, stomach, bladder, etc.
- Parasympathetic: CALMS DOWN salivary glands, lungs, heart, stomach, bladder, etc.
- Motor pathway: two neurone link from the CNS to target tissues
- Preganglionic neurone
- Postganglionic neurone
3 Adapted from Lectures at the University of Leeds Medical School
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller medicsummaries. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for £2.99. You're not tied to anything after your purchase.
Can Stuvia be trusted?
4.6 stars on Google & Trustpilot (+1000 reviews)
73216 documents were sold in the last 30 days
Founded in 2010, the go-to place to buy revision notes and other study material for 14 years now