Nerve 2 Flashcards
What are the 4 types of neuronal endings?
Synapse Motor end plate Muscle end plate Muscle spindle fibres Sensory endings
What are synapses?
Synapses are regions at the end of some axons that transmit the nerve impulse from one neuron to another
What are gap junctions for?
To allow ions and electrical charge to flow through
What is a motor end plate?
Several neuromuscular bulbs that sit within a trough on the muscle fibre surface
What is a neuromusclar junction?
A chemical synapse formed by the contact between a motor neuron and a muscle fibre
What occurs at the neuromuscular junction?
Motor neuron is able to transmit a signal to the muscle fibre causing muscle contraction
Examples of some toxins that act on neuromuscular junctions?
Botulinum toxin tetanus toxin nerve gas latrotoxin snake venom
What does botox do?
blocks acetylcholine release at neuromuscular junction which inhibits contraction
What is a muscle spindle?
acts as a proprinoceptors providing the CNS with data about the musculoskeletal system
What is the role of the muscle spindle?
To maintain posture and regulate the activity of opposing muscle groups involved in motor actvivities such as walking
What causes the changes in the length of the muscle fibre?
Body movements are detected by muscle spindles and the sensory nerves relay this information to the spinal cord
What is the stretch reflex?
When the impulse tells the muscle to contract with greater force in order to decrease the speed at which the muscle is being stretched.
What does the oligondendrocyte do?
Forms the the myelin sheath for several axons insulating the axons and facilitating nerve impulses
What is the most numerous cell of the CNS?
Astrocytes
What are the two types of astrocytes?
Fibrous (white matter)
Protoplasmic (grey matter)
What are the functions of the astrocytes?
Blood brain barrier
Restraint of spread of electrical disturbance by absorption of K+ ions around synapses, unmyelinated axons and nodes of ranvier
What are ependymal cells?
Low columnar epithelial- like cells, lacking basement membranes, which line the cavities of the CNS
What are microglia?
Originate from blood monocytes- small elongated cells with irregular processes. When activated they become small macrophage cells and antigen presenting cells of the CNS mediating immune defence activity
What are the glial cells of the CNS?
Oligondendrocytes
Astrocytes
Ependymal cells
Microglia
What are the glial cells of the PNS?
Schwann Cells
Satellite cells
What are schwann cells?
Enclose all axons of nerves of the PNS producing myelin sheaths around large diameter axons.
What are satellite cells?
Aggregated sensory or automatic neuronal bodies, where they enclose each perikaryon and regulate its microenvironment
What are the meninges?
The membranous covering of the brain and spinal cord
What are the three layers of the meninges?
Dura mater
Arachnoid
Pia mater
What are the functions of the meninges?
Provide a supportive framework for the cerebral and cranial vasculature
Acting with cerebrospinal fluid to protect the CNS from mechanical damage
Involved in cerebral pathology as a common site of infection and intracranial bleeds
What is the dura mater?
Dense CT continuous with periosteum of skull
What is the arachnoid mater?
2 components: a layer in contact with dura mater and a system of trabeculae connecting the layer with the pia mater. The cavity between the trabeculae is the subtracted space filled with CSF
What is the pia mater?
Loose CT containing many blood vessels and covered vy squamous cells.
Very thin and tightly adhered to the surface of the brain and spinal cord
What is the choroid plexus?
The choroid plexus is a collection of cells that produce the cerebrospinal fluid in the ventricles of the brain.
What does the choroid plexus consist of?
Modified ependymal cells
How many choroid plexuses are there and where are they?
Four choroid plexus in the brain and one in each ventricle
What is the functions of the cerebrospinal fluid?
Bouyancy Protection Preventation Homeostasis Clearing waste
What is hyrdocephalus?
Abnormal accumulation of CSF “ water on the brain”
