The Nervous System Flashcards
Anatomical Images
Images from human cadavers illustrating anatomy.
Neurons
Fundamental cell unit of the nervous system.
Action Potential
Electrical impulse traveling along a neuron’s axon to the terminals so neurotransmitter is released at synapse.
Neurotransmitter
Chemical released into the synapse that initiate another action potential in the post synapse of another neuron
Neuroanatomy
Study of the structure of the nervous system.
Sensory Neurons
Neurons that receive sensory input from receptors.
Interneurons
Neurons that process and relay information.
Motor Neurons
Neurons that activate muscle effectors.
Central Nervous System (CNS)
Brain and spinal cord; main control center.
Peripheral Nervous System (PNS)
Nerves outside the CNS; connects to body.
PNS and CNS neurones are…
Bundled into “nerve fibres”
Nerve Fibres
Axons bundles together (potentially 1m long), including mylinated and unmyliated axons
Innervate
To stimulate
Dermatomes
Innervation patterns of the spinal nerves - body regions innervated by specific spinal nerves (CTLSC)
What is the general direction of correspondance of dermatomes to the spinal cord?
Top down. But this isn’t always the case as Cervical and Thoracic nerves are present in the arms, not just the neck and chest
What is needed for linking symptoms to site of spinal cord injury?
Sensation and motor control mapping to specific sections of the spinal cord
Spinal Nerves
31 pairs of nerves exiting the spinal cord to innervate regions of the body
C T L S C
The 5 sections the spinal nerves are split into.
- Cervical (C1-C8)
- Thoracic (T1-T12)
- Lumbar (L1-L5)
- Sacral (S1-S5)
- Coccygeal (C0)
What and where is the Cauda equina?
A bundle of nerves beginning in the middle of the lumbar region of the spine which are separated and control the bladdar, anus, leg and perineum.
Cranial Nerves
12 pairs of nerves directly from the brain.
What makes certian spinal injuries more severe?
Increases severity of damage up the spinal cord could lead to paralysis and loss of breathing ability as they are closer to the brain.
Vagus nerve
A cranial nerve that controls autonomic function
Olfactory (I) nerve
A sensory cranial nerve for smell
Audition
Ability to hear is controlled by cranial nerves (vestibulocochlear)
Paraplegia
Paralysis of the lower half of the body
Quadriplegia
Paralysis below the neck
Afferent Branch
Sensory branch responsible for sensation.
Efferent Branch
Somatic motor branch responsible for movement control.
Sensorimotor circuit
network of neurons in the spinal cord and brain that allows organisms to sense and respond to their environment. Contains sensory “afferent branch” and somatic (part of efferent) branch.
Reflexes
Automatic responses to stimuli, bypassing conscious control (some subconcious perception of pain).subconscious
Are motor neurons part of the CNS or PNS?
Their cell body is in the CNS but they are still part of the PNS
What neurones are involved in a reflex?
Sensory and motor. Sometimes a relay (interneuron) is involved.
Dorsal root ganglion
Cluster of sensory neuron cell bodies that transmits sensory information from the body to the spinal cord from the afferent axon
Ventral root
part of the spinal nerve that transmit motor signals from spinal cord to the PNS and then effector (skeletal muscle)
Two main sensorimotor tracts in spinal cord
Spinothalamic and Pyrimidal
Spinothalamic Tract
Afferent (so type of sensory) pathway for pain (nociception), temperature, and light touch.
Pyramidal Tract
Efferent (so consists of motor neurons) pathway for voluntary muscle control from the brain
How does a light signal from the afferent branch reach the brain for processing?
Via the spinothalamic tract.
1. Sensory neurons cross to the contralateral side of spinal cord
2. Accending sensory fibres pass up via the medulla to the thalamus (this relays sensory information to the cortex)
3. Neurones pass from thalamus to the somatosensory areas of brain (thalamus) to process the sensory information
How does a signal from the efferent branch reach an effector?
Via the pyramidal tract.
1. Upper motor neurons from the motor cortex project to the medulla
2. Motor neurons cross at the medulla to the contralateral side
3. Lower motor neurons exit the spinal cord to control skeletal muscle
Neurotransmitters
Chemicals released at synapses to transmit signals.
What do the symptoms of damage to the NS reflect?
Anatomical location of the damage
Individuals with Brown-Sequard syndrome have damage on one side of their spinal cord but symptoms on both sides of the body. Explain.
lost pain, temp& light touch on contralateral ,lost motor on ipsilateral
The damage interrupts both the spinothalamic and pyramidal tracts. The sensory neurons on one side of the body are unable to cross over and reavh the thalamus of the brain, hence loss of sensation on the contralateral side.
The motor neurons are unable reach the effectors on the same side henc loss of motor function on the ipsilateral side.
Homeostasis
Regulation of internal environment for stability.
Negative Feedback
Process to counteract changes in the body.
Sensorimotor Circuits
Connections between sensory input and motor output.
Dorsal Root
Pathway for sensory neurons entering the spinal cord.
Ventral Root
Pathway for motor neurons exiting the spinal cord.
Corticospinal Tracts
Upper motor neurons controlling voluntary movements.
Interneurons in Reflexes
Process sensory input before activating motor output.
Neural Communication
Involves electrical impulses and chemical signals.
Lower motor neurons
Neurons that exit spinal cord to control muscles.
Somatosensory areas
Brain regions processing sensory information.
Hemi-section
Half-cut of spinal cord
Ipsilateral loss
Loss of function on the same side as injury.
Contralateral loss
Loss of function on the opposite side of injury.
Sympathetic nervous system
Prepares body for ‘fight or flight’ responses. Originates from thoracic-lumbar spine and has chain ganglia
Examples of fight or flight symptoms by SNS
- Increased heart and breathing rate
- Inhibited digestion
- Glucose release
- Blood flow redirection to heart, lungs and muscles (vasoconstriction)
Chain ganglia
Collection of sympathetic neuron cell bodies just outside the spinal cord.
Parasympathetic nervous system
Restores body to resting state after stress. Originates from cranaial nerves and sacral spine. It’s ganglia are next to target organs - no chain ganglia.
Ganglia
Collection of nerve cell bodies that are closely related. Eg ganglia of parasympathetic NS and chain ganglia of sympathetic NS.
Preganglionic neurons
Neurons before the ganglia in ANS pathways.
Postganglionic neurons
Neurons after the ganglia in ANS pathways.
Vagus nerve
Key parasympathetic nerve influencing organ function.
Acetylcholine
Neurotransmitter used by preganglionic ANS (sympathetic and parasympathetic) fibers.
Noradrenaline
Neurotransmitter used by postganglionic sympathetic fibers.
Dynamic homeostasis
Balance maintained by sympathetic and parasympathetic systems.
Why is the ANS an important drug target?
It regulates organ systems
Beta-blockers
Drugs that block noradrenergic receptors to reduce anxiety by reducing the effects of the sympathetic nervous system (blood pressure).
How do all the branches of the Nervous System interact?
gawefky
Lesions
Kind of damage causing dysfunction in sensorimotor or autonomic systems. The effect dependent on location
Lateral lesion
Pyramidal tract (motor) function spared
Medial lesion
Pyramidal tract impaired
Medullary syndrome
Condition often caused by stroke of arteries supplying medulla affecting medulla.
Mellulary Syndrome symptoms
- Vertigo
- Impaired facial sensorimotor control
- Autonomic dysfunction (pupil constriction, eyelid drooping, lack of facial sweating)
Cranial nerves
Nerves originating from the brainstem, involved in ANS.
Thoracic-lumbar spine
Origin of sympathetic nervous system fibers.
Cranial and sacral spine
Origin of parasympathetic nervous system fibers.
Sensorimotor processing
Integration of sensory input and motor output.
Physiological anxiety symptoms
Physical manifestations of anxiety managed by medications.
