Lecture: Anatomy 7: Nervous system Flashcards
What are neurons?
Functional units of the nervous system
What are neuroglia?
Organelle that support neurons
What are the structural components of neurons?
Soma/cell body, dendritic tree, axon hillock, axon/nerve fibre, and axon terminal
What is the purpose of the soma/cell body?
Contains the nucleus and is responsible for the synthesis of proteins/ion channels and important in cellular metabolism.
What is the purpose of the dendritic tree?
Receives input and coveys information towards the stoma.
What is the purpose of the axon hillock?
Origin of the axon
What is the purpose of the axon/nerve fibre?
Transmits action potentials
What is the purpose of the axon terminal?
Where neurotransmitter is released across synaptic cleft.
How are different neurons classified?
Classified based on number of axons/dendrites.
What are unipolar neurons?
Neurons with only one axon Eg. Primary sensory neurons
What are bipolar neurons?
Neurons with one axon and one dendrite Eg. Specialized sensory neurons
What are multipolar neurons?
Neurons with one axon and multiple dendrites Eg. Motor neurons and Autonomic ganglia
How does nerve fibre myelination effect propagation of action potentials?
Myelination allows for saltatory conduction which allows for the propagation of action fibres from node to node.
What are the gaps within the myelin sheath known as?
Nodes of Ranvier
What does the term afferent mean?
Movement of information within axon to the central nervous system.
What does the term efferent mean?
Movement of information within axon away from the central nervous system.
What are synapses?
Junctions between axon terminals and target cells
What are the 2 types of synapses?
- Electrical synapses
2. Chemical synapses
How do chemical synapses work?
Depolarisation of presynaptic membrane opens Ca+ channels which vesicles to fuse with the membrane and release neurotransmitter across the synapse.
What are the 3 main types of neuroglia in the central nervous system (CNS)?
Astrocytes, oligodendrocrytes and microglia
What are astrocytes?
Neuroglia in the CNS that provides structural support of the brain, supply scaffold for neurons in development, maintain ionic environment, and repair the nervous system.
What are oligodendrocytes?
Neuroglia in the CNS that myelinate multiple axons.
What are microglia?
Neuroglia in the CNS that promote repair and house immune cells that secrete cytokines and are involved in phagocytosis.
What neuroglia are found in the peripheral nervous system (PNS)?
Schwann cells
What is the role of Schwann cells?
Schwann cells myelinate axons (one Schwann cell myelinates one axon), house immune cells, and aid in regeneration of neuron axons.
What is the central nervous system composed of?
Brain and spinal cord
What is the role of the peripheral nervous system?
Communication between the CNS and periphery (eg. skin, glands and vessels)
What are the 3 regions of the brain?
Forebrain, midbrain and hindbrain.
What components are found in the forebrain?
Cerebral hemispheres, thalamus, and hypothalamus.
What components are found in the midbrain?
Brainstem
What components are found in the hindbrain?
Cerebellum
What is the function of the cerebral hemispheres?
To process motor and sensory information
What are the 4 lobes of the cerebral hemispheres?
- Frontal lobe
- Parietal lobe
- Temporal lobe
- Occipital lobe
What is the role of the frontal lobe?
Primary motor cortex
What is the role of the parietal lobe?
Primary somatosensory cortex (pain, touch and proprioception)
What is the role of the temporal lobe?
Primary auditory and olfactory cortex
What is the role of the occipital lobe?
Primary visual cortex
What is the function of the thalamus?
Relay centre of the brain; sensory information passes via the thalamus before reaching the cortex
What is the function of the hypothalamus?
Important in homeostasis as it controls the autonomic nervous system and endocrine system
What is the function of the brain stem?
Connects cortex to spinal cord and controls respiration and the cardiovascular systems
What is the function of the cerebellum?
Coordinates muscular activity
What is the function of the spinal cord?
Conveys information and is involved in reflexes.
What are the 5 segments of the spinal cord?
- Cervical
- Thoracic
- Lumbar
- Sacral
- Coccygeal
What are the 2 components of the peripheral nervous system?
- Somatic (voluntary) component which supplies skeletal muscles and skin
- Autonomic (involuntary) component which supplies viscera, smooth muscle, glands and vessel.
Where do peripheral nerves arise from?
Brain/brainstem as cranial nerves or spinal cord as spinal nerves.
What is the role of spinal nerves?
Spinal nerves provide motor and sensory information supply to whole body, except head and parts of neck, and also provide sympathetic autonomic supply to whole body.
How many pairs of spinal nerves are there?
31 pairs
What are the 31 pairs of spinal nerves?
8- cervical nerves which supply upper limb/head/neck
12- thoracic nerves which supply thorax and abdomen
5- lumbar nerves which supply pelvis and lower limbs
5- sacral nerves which supply lower limbs
1- coccygeal nerve
How do the spinal nerves connect to the spinal cord?
Spinal nerves connect to the spinal cord via nerve roots, which are within the vertebral canal, and are composed of ventral and dorsal roots.
What does the ventral root do?
Movement of information away from the spinal nerves
What does the dorsal root do?
Movement of information to the spinal nerves.
What do the spinal nerves branch into?
Primary radi
Dorsal/posterior primary ramus
Ventral/anterior primary ramus
What do the dorsal primary rami supply?
Skin over paravertebral gutter
Erector spinae muscles
Facet joints of vertebral column
What do the ventral primary rami supply?
Supply rest of the body (except head/parts of neck) and form intercostal nerves and four nerve plexuses.
What is the nerve plexus?
Area where ventral primary rami merge to form nerves that contain axons from multiple spinal nerves.
What are the 4 nerve plexuses?
Cervical, brachial, lumbar and sacral plexus.
Why are nerve plexuses important?
Important for innervation of limbs as composed of large muscle groups
What is a dermatome?
An individual strip of skin innervated by a single spinal nerve.
What is a myotome?
An individual muscle group innervated by a single spinal nerve.
How are dermatomes and myotomes formed?
Dermatomes and myotomes develop from somites which are paired blocks of mesoderm that form horizontal bands.
Where does the nervous system derive from?
Nervous system derives from ectoderm
How are intercostal nerves formed and what dermatome do they innervate?
Intercostal nerves are formed by the ventral primary ramus of T1-T11 spinal nerves and innervate T1-T11 dermatomes
Where does the T10 dermatome cross?
The umbilicus
What causes referred pain?
Convergence of imputs into spinal cord often causes referred pain in the dermatomes of the skin, eg. With MI, there is referred pain in the left arm due to converge of spinal nerves.
What is the autonomic nervous system?
Involuntary part of the peripheral nervous system that regulates operation of the internal organs to maintain a constant internal environment.
What does the ANS innervate?
Innervates smooth muscle, cardiac muscle, and glands.
What are the 2 divisions of the ANS?
Sympathetic (“fight or flight”) and parasympathetic (“rest and digest”)
What is the origin of the sympathetic nervous system?
Thoracic/lumbar spinal cord
What is the origin of the parasympathetic nervous system?
Brainstem and sacral spinal cord
How is the autonomic nervous system supplied?
Usually by two neurons (pre and post-ganglionic neurons) to effector organs (such as smooth muscle, cardiac muscle and glands), except sympathetic supply to adrenal medulla which only uses preganglionic neurons.
What does the sympathetic nervous system trigger?
Cardiac muscle (increase heart rate and force of contraction)
Bronchi of lungs (dilate to increase air into lungs)
Sweat glands (increase sweating)
Hair follicles (piloerection)
Blood vessels (constrict blood vessels in skin and organs; more blood to brain and skeletal muscles)
Abdomino-pelvic viscera (inhibit peristalsis and gastric secretions)
Eye (dilates pupils)
How is the sympathetic division supplied?
Axons exit via ventral roots to enter the spinal nerves. Preganglionic axons then enter the sympathetic trunk to either go to postganglionic neurons via primary rami to musculoskeletal system
or branches to heart, lungs or head.
Some preganglionic axons pass through the sympathetic trunk and enter splanchnic nerves to prevertebral ganglia in the abdomen.
What does the parasympathetic nervous system trigger?
Cardiac muscle (decrease heart rate and contraction)
Bronchi of lungs (narrow)
Abdomino-pelvic viscera (stimulates peristalsis and gastric secretions)
Eye (constricts)
Salivary glands (secretion of saliva)
How is the brainstem parasympathetic division supplied?
Preganglionic neurons pass through cranial nerves to postganglionic neurons in ganglia located close to effector organs (pupils, lacrimal glands, and parotid/submandibular glands). Preganglionic axons also enter the vagus nerve to reach the thoracic / abdominal viscera.
How is the sacral parasympathetic division supplied?
Cell bodies of the preganglionic neurons in the sacral spinal cord pass through pelvic splanchnic nerves and synapse with postganglionic neurons on the pelvic organs.
