Nervous System Flashcards
Order of flow of info in the PNS
Receptors-> sensory nerves -> spinal cord/ brain -> motor nerve -> muscle/ internal organ
What are the 3 ways of classifying receptors
- Location (body surface/ internal organs
- Types of stimulus detected (pain/temp)
- Structure (free/encapsulated)
What’s motor endings
Axon terminals of muscle neurones - Usually ACh - Can be norepinephrine at visceral muscle and glands
What at the two components of peripheral nerves
Efferent neurones
Describe afferent neurones
- Sensory neurones
- Axons enter spinal cord through dorsal roots
- TOWARDS the CNS
Describe efferent neurones
- Motor neurones
- Leave spinal cord through ventral roots
- AWAY from CNS
How many nerves at each spinal level
Cervical: C1-C8 Thoracic: T1-T12 Lumbar: L1-L5 Sacral: S1-S5 Coccygeal: Co1
Two enlargements in spinal cord?
Where many nerves enter/ exit
Describe spinal nerves
- Contains a mix of sensory and motor
- Sensory enter Dorsal root
- Motor exit ventral root
- Afferent neurones in dorsal root have cell bodies in dorsal root ganglion
Two party’s of nervous system
Somatic: skin, skeletal muscle, joints. Somatic sensory(afferent) / somatic motor(efferent)
Visceral: emotional reactions
Can be sympathetic or parasympathetic
Main difference in pathway of visceral and somatic
Visceral:
Visceral motor neurone-> down spinal cord-> preganglionic neurone -> synapse at autonomic ganglia-> ganglion of neurones
Define Dermatomes
Area of skin innverated by branches of a signal spinal nerve
Define myotomes
A group of muscles innverated by a single nerve root
6 steps to a sensory pathway
- Adequate stimulus
- Receptor
- Primary sensory neurone
- Sensory nucleus
- Thalamus
- Primary sensory cortex
3 things that mediate receptors
- Modality (visual, mechanical)
- Intensity- sensory threshold
- Duration - adaptation
Define sensory threshold
Smallest intensity at which a sensation is detected
Define adaptation
Intensity diminishes when stimulus is continuous for a period of time
Describe receptive fields
- The area that activates a receptor/ sensory neurone
- High receptor density means small receptive fields
- Overlapping receptive fields allows sensory discrimination
Define cortical magnification
Cortical maps are distorted are distorted in proportion to density of peripheral innervation/ density of receptors
Define lateral inhibition
This is done by sensory neurones having inhibitory synapses with neighbouring neurones, thus amplifying difference in activity of neurones
Describe the role of the thalamus in sensation
- Nuclei process and modify information
- connections contain a mixture of serial and parallel processing
What are cortico-fugal fibres
These filter ascending information
-
Perception therefore differs from sensation
Divergence in connectivity as cortex is reached
Primary sensory cortex-> sensory association cortex-> polysensory association cortex
Conscious level info travels in two main tracts:
- Dorsal (posterior) column/ medial lemniscus (touch)
2. Anterolateral system tracts (pain)
