INTS 6: Introduction to Nervous and Musculoskeletal Systems Flashcards
What is the nervous system?
What is the nervous system comprised of?
Very briefly describe their function
- central nervous system (CNS) :
- brain
- spinal cord
- peripheral nervous system (PNS) :
- cranial peripheral nerves
- spinal peripheral nerves
- these help carry out sensory and motor functions
Where do cranial nerves arise from?
- the brain and brainstem
Where do spinal nerves arise from?
- the spinal cord
What type of neurons are most cranial and all spinal nerves made up of?
- they are made up of axons of both motor and sensory neurons
What pathways does the PNS use to send/relay information?
- relaying information back to CNS:
- sensory/afferent/ascending pathways
- sending information from CNS to the rest of the body:
- motor/efferent/descending pathways
- motor pathways can be further divided into somatic (voluntary) and autonomic (involuntary) components
- observe diagram
Observe the diagram and define these orientation terms
- ventral and dorsal change along the course of the nervous system
- rostral:
- anything toward the anterior pole of the brain
- caudal:
- anything toward the inferior pole of the spinal cord
Observe this diagram of the different planes of orientation
- this will be further explained in later sessions
What is the part of the CNS housed within the cranial cavity called?
- the brain
Describe the surface features of the brain
- ridges: called gyri
- grooves: called sulci
- larger grooves: called fissues
Describe the divisions of the brain
- comprised of the forebrain:
- cerebral hemispheres
- hypothalamus
- thalamus
- midbrain
- hindbrain:
- pons
- medulla
- cerebellum
Describe the lobes the cerebral hemispheres are divided into
- frontal
- parietal
- occipital
- temporal
- limbic
- insular
How much of the body’s blood supply does the brain receive?
Compare it to the weight
- 15-20 of the body’s blood supply
- whereas it’s 2% of total body weight
Which two principal sources supply blood to the brain?
Where is the source of these sources?
- internal carotid arteries
- vertebral arteries
- these arteries are indirect or direct branches of the main artery from the heart, the aorta
Describe the Circle of Willis
How do the internal carotid and vertebral arteries supply blood to the brain?
- The internal carotid arteries ascend in the neck and enter the cranial cavity through holes (foramina) in the skull
- The vertebral arteries, as the name suggests, are associated with the bones in the neck, the vertebrae
- The two vertebral arteries join to form the basilar artery, this vertebral-basilar system supplies the brainstem and spinal cord.
- The forebrain receives blood from both the internal carotid and vertebral-basilar systems, which join to form an arterial circle at the base of the brain - the Circle of Willis.
Where do the anterior, middle and posterior cerebral arteries supply?
- The anterior cerebral arteries:
- supply the medial surfaces of the front two thirds of the cerebral hemispheres
- the middle cerebral arteries (extensions of the internal carotid arteries):
- supply most of the lateral surfaces of the brain as well as deep structures
- the posterior cerebral arteries:
- supply the medial surfaces of the posterior one third of the forebrain
What subdivisions form the autonomic nervous system?
- parasympathetic:
- rest and digest
- under ‘normal’ circumstances
- sympathetic:
- fight or flight
- when are body is put into a stressful situation
What are some responses from
- parasympathetic system
- sympathetic
What do sensory neurons do?
- relay information toward the CNS
What do motor neurons do?
- relay information away from the CNS
What types of axons do peripheral nerves carry?
- most peripheral nerves carry a mixture of sensory and motor axons
What is a ganglion?
- a cluster of neuronal cell bodies
Where do cell bodies of sensory neurons reside?
- within the dorsal root ganglia
Where do the cell bodies of motor neurons reside?
- within the ventral horn of the spinal cord
- or within the brain
What are pre-ganglionic neurons?
- neurons with axons which run from the spinal cord or brain to a ganglion
What are post-ganglionic neurons?
- neurons with axons which run from a ganglion to their destination
Where are the pre-ganglionic neurons of the sympathetic and parasympathetic division located?
- sympathetic pre-ganglionic neurons:
- located in the lateral horn of the spinal cord found only in the thoracolumbar region (T1-L2/3)
- parasympathetic:
- located within the brainstem and the sacral region of the spinal cord
What is the function of these structures in a neuron?
- dendrites
- cell body
- axon
- axon terminals
- dendrites:
- receive inputs
- cell body:
- receives and sums imputs
- axon:
- sends inputs to other nerve cells
- axon terminals:
- contact dendrites of other neurons
What part of the neurons provide insulation in:
- the PNS
- CNS
- in PNS:
- Schwann cells:
- contain myelin, surround the axon
- in CNS:
- oligodendrocytes
What are the unmyelinated spaces of neuron called?
- nodes of Ranvier
What are the three types of neuron?
- multipolar
- pseudounipolar
- bipolar
Describe the chracteristics of multipolar neurons
- the most abundant neuronal type
- found in the brian and spinal cord
- have multiple dendrites attached to the cell body (soma) and a single azon arising from the axon hillock
Describe the chracteristics of pseudounipolar neurons
- found mainly in spinal ganglia and receive sensory information from the periphery
- The signal travels along a dendritic axon to the axon, bypassing the cell body
Describe the characteristics of bipolar neurons
- found in the retina and in olfactory epithelium
- Like the pseudopolar neurons, they have a dendritic axon which conveys information to the axon via the cell body
How many times do glial cells outnumber neurons?
- 10:1
What are the different types of glial cells and their functions?
- Microglia:
- play an important role in immune function within the CNS.
- Astrocytes:
- perform a number of supportive functions in the CNS.
- Oligodendrocytes:
- create the myelin sheath surrounding axons in the CNS.
- Schwann cells:
- create the myelin sheath surrounding some axons in the PNS.
- Ependymal cells:
- line the ventricular system and separate the cerebrospinal fluid from the neural tissue.
- Polydendrocytes:
- are stem cells within the brain which can generate both glial cells and neurons.
What are the two ways communication occurs between neurons at synapses?
- electrical:
- ions move directly between neurons at gap junctions
- chemical:
- neurotransmitters convey the signal from one neuron to another
What are the main types of synapses?
- Axodendritic:
- these are the most common form of synapse
- The dendritic tree of the neuron receives many thousands of inputs from axons
- The organisation and function of the dendritic tree determines the convergence of signals.
- Axosomatic:
- the axon of one neuron can connect to the soma of the post-synaptic neuron
- Less common than axodendritic synapses.
- Axoaxonic:
- the axon of one neuron connects at or near to the axon hillock of the post-synaptic neuron.
What is the skeleton made up of?
- the bones
- cartilage
What do muscles consist of?
- muscle fibres
- blood vessels
- nerve fibres
- connective tissue
What are the six major functions of the musculoskeletal system?
- producing movement
- maintaining posture
- stabilising joints
- producing heat
- protection:
- hard bone tissue defends soft organs from damage
- mineral storage:
- bones are a repository of key minerals:
- calcium, phosphorus, sodium, magnesium
What are the two major types of muscle?
- striated muscle:
- separated into:
- skeletal
- cardiac
- smooth muscle
Briefly describe the function and structure of skeletal muscle
- attach two or more bones
- facilitate movement at a joint
- it is striated
- it is under voluntary control
Briefly describe the structure, location and function of smooth muscle
- found in the walls of blood vessels, the digestive, urinary, respiratory and reproductive systems
- Smooth muscle pushes substances through these organs, e.g. smooth muscle in the walls of blood vessels pushes blood around the body
- The muscle tissue does not have striations, like skeletal and cardiac muscle, hence the name ‘smooth’ muscle.
- The contractions of smooth muscle fibres are slow and sustained.
- Smooth muscle is not under voluntary control.
Briefly describe the structure and function of cardiac muscle
- present in the heart and is responsible for the continued beating of the heart throughout life
- cardiac muscle is striated, like skeletal muscle
- but is not under voluntary control
Explain the properties of muscles
- excitability:
- Muscle tissue receives chemical stimulation from the nervous system
- This results in generation of an electrical impulse that travels around the muscle fibres and causes them to contract
- contractility:
- refers to the muscle’s ability to shorten following stimulation
- It is important to note that while muscle contraction can result in muscle shortening, muscle contraction does not necessarily result in a net change in muscle length
- extensibility:
- refers to the ability of muscle fibres to be stretched or extended, when they are relaxed.
- This is necessary to allow opposing movements at joints.
- For example, if a muscle crossing the front of a joint is shortening to produce a movement, then the muscle crossing the back of the joint must be able to be stretched.
- elasticity:
- reflects the requirement for a muscle to recoil to its resting length after being stretched
What are the characteristics of the bones and cartilage?
- yellow is bone
- blue is cartilage
- bone tissue:
- rigid
- hard to break
- cartilage:
- provides cushioning
- support the bones of the skeleton
What causes movement?
- the muscles attached to the skeleton allow us to move
- muscles attach to bones across joints
- factors that influence range of movement:
- shape of the bones at the joints
- location of the muscle attachments
- size of muscle
