phy2011

• Neurones in the mesencephalic locomotor region send axons that influence, directly or indirectly, the spinal interneurones, thereby determining the rhythm of locomotion.
• The phasic stretch reflex or tendon jerk in response to a tendon tap is the result of excitation of the primary endings of muscle spindles by the brief stretch applied to the tendon.
• The setting of the gain or ‘stiffness’ of spinal reflexes is largely a function of descending (upper) motor neurons
• The main function of the Ia inhibitory neuron is to inhibit antagonist motor neurons
• A likely cause of spasticity that develops following an upper motor neuron lesion is increased alpha-gamma coactivation
• Autonomic Nervous System (ANS)


  Functions not normally under conscious control, e.g. homeostasis, heart rate/blood pressure, smooth muscle contraction, pupil diameter, sweating
• Disruption of autonomic functions can be life-threatening
• Autonomic functions


  Controlled either directly via ANS neural control, or indirectly via the endocrine system (hormones)
• Autonomic Nervous System


  • Widespread mechanisms to coordinate a number of structures at a time
  • Loop: output (motor neurons to tissues), controller (descending input from higher brain to ANS brainstem controllers to motor neurons), and feedback (sensory from tissues to all others)
• Motor (Efferent) Arm of the ANS


  Sympathetic (fight, flight, or fright) and parasympathetic (rest, recover, and relax)
• Motor (Efferent) Arm of the ANS


  Runs from CNS to ganglion via pre-ganglionic neuron, where it synapses on the post-ganglionic neuron to smooth muscle, glands, and cardiac muscle
• Parasympathetic


  • Pre-ganglionic neurons are located in the brainstem (cranial nerves) and the bottom of the spine (sacral nerves)
  • The ganglion is found in or very close to the target tissue
  • Vagus nerve (cranial nerve X) is the only one of the parasympathetic pre-ganglionic neurons that has widespread control over many organs
• Parasympathetic


  • Midbrain CN III - pupil aperture and lens accommodation
  • Pons CN VII - lacrimal (tear) glands, submandibular & submaxillary (salivary) glands
  • Medulla CN IX - glossopharyngeal parotid gland (salivary)
• Sympathetic


  • Outflow from rest of spinal cord (centre), thoracic and lumbar regions (T1 - L3)
  • Ganglia are right next to the spinal cord, immediate synapse at the para-vertebral ganglia lying in a 'chain' beside spinal cord, also called the sympathetic chain ganglia
  • Chain extends from upper neck down to coccyx
• Controller (Descending Input)


  • Critical regions are the Hypothalamus (integrative control) and Medulla (reflexive control)
  • Both receive higher input from cortex, limbic system, and thalamus
• Descending Input


  • Cortex --> when wanting to exercise, HR increases, redirection of blood, all occur as you begin exercise (not after!!)
  • Cortex + limbic system --> meditation - decrease in HR, force of contraction, respiration, etc. sight - sexual arousal - increase in HR, respiratory rate, etc
  • Cortex + thalamus --> sight/smell of food causes salivation
• Hypothalamus


  • Collection of nuclei directly below the thalamus, responds and integrates various inputs
  • Links nervous system to endocrine system via pituitary gland
  • Controls body over moderate time scales (ANS) and long time scales (endocrine)
  • Para-ventricular nucleus (PVN) - one on either side of ventricle, it is the only brain system in closed reflex with both ANS divisions (sym/parasym)
• Medulla


  • 'Automatic' output controller
  • Packed with many nuclei that are part of the ANS pre-ganglionic neurons of the parasympathetic pathway
  • Rostral Ventrolateral Medulla (RVLM) = CVS (cardio-vascular system) excitation; Caudal Ventrolateral Medulla (CVLM) = CVS inhibition
• Feedback System


  • Reflexive rapid responses that happens unconsciously
  • Internal organs - non-discriminative feedback
  • Pathway of nociceptors is the same as somatosensory system - cell body in dorsal root ganglion (DRG), synapses in 2nd order neuron that crosses to other side, to ascending ventrolateral nerve tracts
  • Rest of pathway is also the same, SC - thalamus - cortex - intralaminar and VM nuclei
  • Vagus nerve (CN X) carries most mixed sensory & motor nerves, providing a huge amount of non-nociceptive ANS sensory information
  • Non-nociceptive sensory information flows to Nucleus Tractus Solitarius (NTS) in medulla (2nd order neurons located here) (does NOT synapse in gracile/cuneate thus discriminative and non-discriminative input are never mixed
  • After this point, information is crossed between both parts of the brain and is sent up to the higher regions
• Sensory and motor cortex lie adjacent to one another.
• The main function of the vestibulocerebellum is Co-ordination of agonist and antagonist muscles for postural control of the axial skeleton
• The cerebrocerebellum Would be more important in learning tennis, where coordination of rapid, complex movements involving the whole body is important
• The main output cell of the cerebellar cortex is the purkinjke cell
• Ventral posterior nucleus of thalamus is NOT part of the basal ganglia
• the function of the basal ganglia is Selection of desired motor programs and suppression of undesired ones
• Parkinson's disease results from a dopamine deficiency that results in excessive inhibition of the thalamus
• Autonomic Nervous System (ANS)


  Functions not normally under conscious control, e.g. homeostasis, heart rate/blood pressure, smooth muscle contraction, pupil diameter, sweating
• Autonomic functions


  • Disruption can be life-threatening
  • Controlled either directly via ANS neural control, or indirectly via the endocrine system (hormones)
  • Widespread mechanisms to coordinate a number of structures at a time
• Autonomic Nervous System (ANS) control loop

  1. Output (motor neurons to tissues)

  2. Controller (descending input from higher brain to ANS brainstem controllers to motor neurons)

  3. Feedback (sensory from tissues to all others)
• Motor (Efferent) Arm of the ANS


  Sympathetic (fight, flight, or fright) and parasympathetic (rest, recover, and relax)
• Parasympathetic pathway


  1. Pre-ganglionic neurons located in brainstem (cranial nerves) and bottom of spine (sacral nerves)

  2. Ganglion found in or very close to target tissue

  3. Vagus nerve (cranial nerve X) has widespread control over many organs
• Parasympathetic control of specific structures

  • Midbrain CN III - pupil aperture and lens accommodation
  • Pons CN VII - lacrimal (tear) glands, submandibular & submaxillary (salivary) glands
  • Medulla CN IX - glossopharyngeal parotid gland (salivary)
• Sympathetic pathway


  1. Outflow from rest of spinal cord (centre), thoracic and lumbar regions (T1 - L3)

  2. Ganglia are right next to the spinal cord, immediate synapse at the para-vertebral ganglia lying in a 'chain' beside spinal cord, also called the sympathetic chain ganglia
• Controller (Descending Input)


  • Critical regions are the Hypothalamus (integrative control) and Medulla (reflexive control)
  • Both receive higher input from cortex, limbic system, and thalamus
• Descending input examples


  • Cortex --> when wanting to exercise, HR increases, redirection of blood, all occur as you begin exercise (not after!!)
  • Cortex + limbic system --> meditation - decrease in HR, force of contraction, respiration, etc. sight - sexual arousal - increase in HR, respiratory rate, etc
  • Cortex + thalamus --> sight/smell of food causes salivation
• Hypothalamus


  • Collection of nuclei directly below the thalamus, responds and integrates various inputs
  • Links nervous system to endocrine system via pituitary gland
  • Controls body over moderate time scales (ANS) and long time scales (endocrine)
  • Para-ventricular nucleus (PVN) - only brain system in closed reflex with both ANS divisions (sym/parasym)
• Medulla


  • Packed with many nuclei that are part of the ANS pre-ganglionic neurons of the parasympathetic pathway
  • Rostral Ventrolateral Medulla (RVLM) = CVS (cardio-vascular system) excitation; Caudal Ventrolateral Medulla (CVLM) = CVS inhibition
• Feedback System


  • Reflexive rapid responses that happens unconsciously
  • Internal organs - non-discriminative feedback
• Nociceptive feedback pathway


  1. Pathway of nociceptors is the same as somatosensory system - cell body in dorsal root ganglion (DRG), synapses in 2nd order neuron that crosses to other side, to ascending ventrolateral nerve tracts

  2. Rest of pathway is also the same, SC - thalamus - cortex - intralaminar and VM nuclei
• Vagus nerve (CN X)


  • Carries most mixed sensory & motor nerves, providing a huge amount of non-nociceptive ANS sensory information
  • Non-nociceptive sensory information flows to Nucleus Tractus Solitarius (NTS) in medulla (2nd order neurons located here) (does NOT synapse in gracile/cuneate thus discriminative and non-discriminative input are never mixed)