Nervous System - Somatic and Autonomic Nervous Systems Flashcards
sensory nervous system
provides info to the CNS about what’s happening in the external environment
- PNS to CNS
components of sensory nervous system
- sense organ
- receptors (specific stimulus for specific receptors)
- pathways to CNS
- parts of brain involved in sensory perception
special senses
- taste, smell, hearing, sight, EQ
- receptors are localized in a particular area
general senses
- pain, tactile, pressure, temperature, and proprioception (position, orientation)
- receptors widely distributed in body
- divided into somatic senses and visceral senses
somatic senses
associated with skin and body in general
visceral senses
associated with internal organs
types of sensory receptors
- exteroreceptors (outside environment)
- interoreceptors (inside environment)
sensory receptors (4)
- mechanoreceptors
- thermoreceptors
- chemoreceptors
- nociceptors
mechanoreceptors
detect changes in pressure or movement
thermoreceptors
detect changes in temperature
chemoreceptors
detect changes in chemical concentration of substances
nociceptors
- detect tissue damage (eg pain)
- only sense receptors that do not adapt!
nocere
“harm”
cutaneous mechanoreceptors (5)
- pacinian corpuscles
- meissner’s corpuscles
- merkel’s discs
- ruffini’s corpuscle
- free nerve endings
pacinian corpuscles
respond to higher frequency vibration and deep heavy pressure
meissner’s corpuscles
respond to lower frequency vibrations and light pressure
merkel’s discs
respond to steady touch - pressure
ruffini’s corpuscle
respond to push or pull on skin
free nerve endings
respond to temperature and pain
sensory modality principles (4)
- labeled line theory
- frequency coding
- population coding
- adaption
labeled line theory
- stimulus recognized by the place the sensory cells excited in the CNS
- tells brain where a stimulus is/ what kind it is
sensory modality = stimulus modality
sensory modality is an identifiable class of sensation
frequency coding
intense stimuli produce a higher frequency of action potentials
population coding
more intense stimuli increase the number of cells that participate
adaption
decrease in sensation that occurs upon continued stimulation
sensory perception
- occurs only after impulses are interpreted by the brain
steps in sensory perception
- stimulus acting on a receptor
- action potential generated,
- impulse conducted to CNS
- impulse translated into info in CNS,
- info interpreted in CNS
- stimulus is PERCEIVED!
ascending sensory pathway
- dorsal column pathways
- touch + proprioception
- spinothalamic tract
- temperature + pain
primary somatosensory cortex: somatotropin representation of of body on cortex
- projections of sensory neurons form a “neural map” of the body
- adjacent areas of the cortex receiving sensory input from adjacent areas of the body
- “point-for-point correspondence of an area of the body to a specific point in the CNS (somatosensory cortex)”
descending motor pathways (pyramidal tracts)
- coritcobulbar tract
- ventral corticospinal tract
- lateral corticospinal tract
corticobulbar tract
supplies motor commands to cranial nerve motor nuclei of the head and neck
(face and tongue)
ventral corticospinal tract
innervates lower motor neurones of the axial and proximal muscles
lateral corticospinal tract
supplies inputs to lower motor neurons controlling the muscles of the distal extremities
neuronal processing of motor programs
- motor activity begins in sensory areas together with premotor areas
- motor control is hierarchical and serial
extrapyramidal system - basal ganglia and cerebellum
- both play important roles in coordination of movement
vestibular apparatus
- sense of balance originates in sensory hairs cels here
- utricles and saccules contain hair cells that respond to static gravity
- ampulla of the three semicircular canals detect acceleration
- afferent info from here is carried over the cranial nerve and projects to the vestibular nuclei in the medulla (down to spinal cord to maintain posture)
general ascending sensory pathways
- stimulus
- sensory organ with receptors
- 1st, 2nd, 3rd, 4th order neurons ascend to brain (somatosensory cortex)
- pyramidal tracts then extrapyramidal tracts
- alpha motor neuron
- muscles
divisions of the autonomic nervous system
- sympathetic (fight or flight)
- parasympathetic (rest and digest)
- enteric nervous system (restricted to gastrointestinal system)
- most organs receive both sympathetic and parasympathetic efferents that usually have opposite effects
functions served by autonomic nervous system
- homeostatic
2. adaptive
control of ANS
- internal functions
- involuntary reflexes
internal functions controlled by ANS
cardiovascular system, digestive, respiratory tract, kidney, etc
involuntary reflexes controlled by ANS
constriction of pupil, vasodilation of skin and sweating with high body temperature, etc
somatic vs autonomic efferents
somatic motor system
- single-neuron efferent pathway
autonomic nervous system
- two-neuron efferent pathway (preganglionic neuron and postganglionic neuron)
sympathetic NS efferents
- sympathetic preganglionic fibers
- short
- orientate from thoraco-lumbar segments
- autonomic ganglia
- para-vertebral ganglia (sympathetic chains)
- pre-vertebral ganglia (unpaired, in abdomen)
- sympathetic postganglionic fibers
- long
- originate in autonomic ganglia
parasympathetic NS efferents
- parasympathetic preganglionic fibers
- long
- originate in the cranial-sacral segments
- autonomic ganglia
- located near or within visceral organs
- parasympathetic postganglionic fibers
- short
neurotransmitters used by PSNS vs SNS
- SNS/PSNS: preganglionic synapse uses acetylcholine (nicotinic receptors)
- SNS: postganglionic synapse uses norepinephrine (alpha and beta receptors)
- PSNS: postganglionic synapse uses acetylcholine (muscarinic receptors)
postganglionic neurons: adrenergic receptors
metabotropic receptors:
- excitatory alpha 1
- inhibitory alpha 2
- excitatory beta 1
- inhibitory beta 2
postganglionic neurons: muscarinic receptors
metabotropic receptors:
- excitatory M1, M3, M5
- inhibitory M2, M4
cortico means
cortex
vagus nerve X
major parasympathetic nerve
