Lecture 1 - Intro to HNN Block Flashcards
What are the two types of cell that make up the nervous system?
Neurons and Glial Cells
What are the main parts of the neuron?
Cell body, axons and dendrites.
What surrounds the nucleus of a neuron?
Extensive rough ER, Golgi apparatus, and mitochondria
What organises the neuronal cytoplasm into different areas?
Neurofilaments (intermediate filaments) and microtubules
What is the function of dendrites?
They receive information from other neurons or from sensory receptors and transmit the information towards the neuron cell body.
What is the axon hillock?
Where the axon leaves the neuron cell body.
How can neurons by classified?
According to their function or their structure.
Describe multipolar neurons
They have many dendrites and a single axon. Most neurons in the CNS and nearly all motor neurons are multipolar.
Describe Bipolar neurons
Bipolar neurons have two processes: one dendrite and one axon. Bipolar neurons are located in some sensory organs, such as in the retina of the eye and in the nasal cavity.
Describe pseudo unipolar neurons.
Pseudo-unipolar neurons have a single process extending from the cell body. This process divides into two processes a short distance from the cell body. One process extends to the periphery, and the other extends to the CNS. The two extensions function as a single axon with small dendrite-like sensory receptor at the periphery.
What are Glial cells?
Glial cells are the primarily supportive cells of the CNS and PNS, meaning these cells do not conduct action potentials. Neuroglia are much more numerous than neurons. Most neuroglia retain the ability to divide, whereas neurons do not..
Name the 6 different types of Glial cell.
- Astrocytes
- Ependymal Cells
- Oligodendrocytes
- Schwann Cells
- Satellite Cells
- Microglia
Describe the function of Astrocytes.
Astrocytes serve as the major supporting cells in the CNS. In this role, astrocytes can stimulate or inhibit the signalling activity of nearby neurons. In addition, astrocytes participate with the blood vessel endothelium to form a permeability barrier, the blood brain barrier, between the blood and the CNS. Astrocytes help limit damage to neural tissue; however, the repair process can form a scar that blocks the regeneration of damaged axons.
Describe the function of Ependymal cells
Ependymal cells line the fluid-filled cavities (ventricles and canals) within the CNS. Some produce cerebrospinal fluid, and others, with cilia on the surface, help move the CSF through the CNS.
Describe the function of Microglia.
Microglia act as immune cells of the CNS. They help protect the brain by removing bacteria and debris.
Describe the function of Oligodendrocytes.
Oligodendrocytes act in the CNS to provide an insulating material that surrounds axons.
Describe the function of Schwann cells.
Schwann cells act in the PNS to provide an insulating material that surrounds axons.
Describe the function of Satellite cells.
They are similar in function to astrocytes. They are small cells that surround neurons in sensory, sympathetic and parasympathetic ganglia, helping to regulate the external chemical environment. They are highly sensitive to injury and inflammation, and appear to contribute to pathological states, such as chronic pain.
Describe the Myelin Sheath.
Myelin sheaths are specialised layers that wrap around the axons of some neurons. They are formed either by the cell processes of oligodendrocytes in the CNS or Schwann cells in the PNS. Axons with a myelin sheath are called myelinated axons.
What is the function of Myelin.
It is an excellent insulator that prevents almost all ion movement across the cell membrane.
What are the nodes of Ranvier?
Gaps in the myelin sheath. They occur about every millimetre between the oligodendrocyte segments or between individual Schwann cells.
What occurs at the nodes of Ranvier?
Ion movement
What does myelination do?
It increases the speed and efficiency of action potential generation along the axon.
What does Grey Matter consist of?
Groups of neuron cell bodies and their dendrites, where there is very little myelin.
What is grey matter on the surface of the brain in the CNS called?
The Cortex
What are clusters of grey matter located deeper within the brain called?
Nuclei
What is a cluster of neuron cell bodies called in the PNS
Ganglion
What is white matter?
Bundles of parallel axons with their myelin sheaths, which are whitish in colour.
What forms nerves?
Bundles of axons and associated connective tissue.
What does the primary motor cortex correspond with?
The pre-central gyrus
What is the pyramidal tract composed of?
The Corticospinal tract and the corticobulbar tract.
What does the corticospinal tract supply?
The musculature of the body
What does the corticobulbar tract supply?
The musculature of the head and neck
From where does the pyramidal tract get its name?
The medullary pyramids of the medulla oblongata.
Where does the pyramidal tract originate?
The cerebral cortex
What are the main language areas of the brain?
Broca’s Area - motor aspect of speech
Wernicke’s Area -understanding of speech
What are people commonly left dominant for?
Speech
What is the blood supply for the area of the brain supplying the leg?
Anterior Cerebral Artery
What is the blood supply for the area of the brain supplying the right side of the body (apart from the leg)?
The left middle cerebral artery.
What causes MS?
Discrete lesions affecting myelin that surrounds many CNS axons and can be seen as plaques in white matter of brain and spinal cord.
What are some of the symptoms of MS?
- Partial loss of vision
- Double vision (altered eye movements)
- Sensory changes (e.g. numbness)
- Motor Symptoms (e.g. weakness ataxia)
Describe spinal nerves
Spinal nerves are nerve fibres that are travelling to/from the limbs from the spinal cord.
When do spinal nerves become peripheral nerves?
One they have passed through plexuses (such as brachial and lumbosacral plexuses).
What is a dermatome?
A region of skin supplied by a single spinal nerve .
What is paraesthesia?
A tingling sensation.
What is affected first in sensory loss?
The longest fibres (stocking and glove distribution). This can occur in conditions such as vitamin B12 deficiency. Long fibres are more metabolically at risk than others
What are the three main anatomically divisions of the ANS?
- Sympathetic
- Parasympathetic
- Enteric
What is the enteric nervous system composed of?
The intrinsic nerve plexuses of the G.I tract. It has sufficient integrative capabilities to allow it to function independently of the CNS.
Is the ANS mainly voluntary or involuntary?
Involuntary
What processes does the ANS regulate?
- Contraction and relaxation of vascular and visceral smooth muscle
- All exocrine and certain endocrine secretions
- The heartbeat
- Energy Metabolism, particularly in the liver and skeletal muscle.
Describe the autonomic efferent pathway.
The autonomic efferent pathway consists of 2 neurons arranged in series.
Describe the somatic motor system
The somatic motor system consists of a single motor neuron connecting the CNS to skeletal muscle fibres.
Where are discrete parasympathetic ganglia found? Give an example of one.
The Head and Neck - the ciliary ganglion.
Where are the cell bodies of sympathetic pre-ganglionic neurons located?
In the lateral horn of the grey matter of the thoracic and lumbar segments of the spinal cord.
Where do sympathetic pre-ganglionic fibres synapse?
In the paravertebral chains of sympathetic ganglia, lying on either side of the spinal cord
What is the exception to the two neuron arrangement in the ANS?
The innervation of the adrenal medulla. The catecholamine-secreting cells of the adrenal medulla are, in effect, modified post-ganglionic sympathetic neurons, and the nerves supplying the gland are equivalent to pre-ganglionic fibres.
What are the parasympathetic cranial nerves? What do they supply?
- Oculomotor Nerve (eye)
- Facial Nerve and Glossopharyngeal Nerve (Salivary Glands and Nasopharynx)
- Vagus Nerve (thoracic and abdominal viscera)
What do the nervi erigentes do?
They are the nerves that are stimulated to evoke a genital erection.
