Cerebellum
- 2 cerebellar hemispheres (vermin in middle)
- cerebellar cortex (gray matter)
- Arbor Vitae (white matter)
- regulation of posture and balance
- coordinate movements
Thalamus
- relay station for sensory and motor information
- crude interpretation of touch, pressure, temp, and pain
- forms walls of 3rd ventricle
- organized into 7 nuclei
Hypothalamus
- located inferior to the thalamus
- regulates body temp, eating and drinking, regulates emotions, regulates diurnal rhythms, other bio drives
- controls and integrates activity of the ANS and pituitary gland=> controls homeostasis
- link between nervous and endocrine system
Epithalamus
1) pineal gland (melatonin)- contributes to setting biological clock
2) habenular nuclei- emotional responses to odors
Pons
- Pontine Nuclei- gray matter centers connecting cerebral cortex and cerebellum-> coordinate voluntary motor output
- Apneustic Area- controls depth of breathing
- Pneumotaxic Area- controls rate of breathing
Medulla Oblongata
- connects brain to spinal cord
- contains cardiovascular center
- control of respiratory rhythmicity
- swallowing, coughing, sneezing, vomiting
Midbrain (mesencephalon)
- Located between pons and the dienchephalon
- Superior and Inferior Colliculi
Internal Anatomy of spinal cord (gray matter)
Central canal: small opening in center of SC; contains CSF
Posterior Horns: cell bodies of somatic and visceral sensory neurons
Gray Commisure: connects posterior horns
Anterior Horns: cell bodies of somatic motor neurons
Lateral Horns: cell bodies of visceral motor neurons; found only in thoracic, lumbar and sacral regions of spinal cord
Internal Anatomy of Spinal Cord (white matter)
Posterior Columns: sensory tracts (ascending)
Lateral Columns: motor and sensory tracts
Anterior Columns: motor tracts (descending)
Anterior White Commisure: connects white matter on the left and right side of SC
Input and Output to Spinal Cord
Dorsal root of spinal nerve: carries afferent information
Dorsal root ganglion: cluster of sensory cell bodies outside the CNS
Ventral root: carries efferent information from anterior portion of cord
Spinal nerves: joining of dorsal and ventral roots; only 2 cm long; mixed nerves both sensory and motor information
Reflexes
- Stretch Reflex: prevents over-stretching, contracts muscle that was stretched, sensed by muscle spindle, monosynaptic, ipsilateral, spinal somatic relfex
- Tendon Reflex: prevent damage from too much tension, inhibition of muscle that is contracting, tension sensed by golgi tendon organ, polysynaptic, ipsilateral, spinal, somatic reflex
- Flexor reflex: purpose to protect body part from further injury, causes flexion of affected limb, pain sensed by nociceptors, polysynaptic, ipsilateral, spinal, somatic relfex
- Crossed Extensor Reflex: stabilize body position when a painful stimulus results in flexion of opposite limb, paired with flexor reflex, extension of opposite limb, pain sensed by nociceptors, polysynaptic contralateral, spinal, somatic reflex
Differences between ANS and Somatic NS
Autonomic Nervous System:
1. effectors- cardiac muscle, smooth muscle, glands
2. control- involuntary (self-governing)
3. Output- two efferent neurons exit CNS.
Somatic Nervous System:
1. Effector- skeletal muscle
2. Control- voluntary
3. Output- one efferent neuron exits the CNS
first efferent neuron exits sc and synapses with another neuron in a ganglion
Differentiate between the parasympathetic and sympathetic NS
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Resting Membrane Potential
- Chemical force (K+ gradient) pushes K+ out
- Electrical force (inside negative) pulls K+ in
-High inside concentration of [K+]
-Low inside concentration of [Na+]
Na,K-ATPase develops and maintains steady-state ion gradients
Channel proteins
- K-leak channel allows for K+ to flow with its gradient and create a negative inside potential
- chemically(ligand)-gated channels= open when a signal molecule binds to the channel protein
- mechanically-gated channels= open when membrane gets stretched
- voltage-gated channels= open when the membrane potential gets less negative (depolarized)
Events of Action Potential
- Local change in membrane potential, such local changes can be hyperpolarizing or depolarizing, ‘graded’ potentials, AP starts w/ depolarization
- Depolarization to a threshold value causes voltage-gated Na-channels within local region to open (positive feedback loop)
- Critical Point: shortly after Na-channels open=> they spontaneously close (inactivation)
- Depolarization also opens a second population of voltage-gated channels (repolarization)
Graded Potential vs. Action Potential
Graded potentials happens in dendrites and cell body of neurons, size varies with strength of stimulus, generated by chemically and mechanically gated channels
Refractory Periods
- Absolute Refractory Period: immediately following inactivation of Na-channels, membrane cannot be restimulated to produce AP (resetting Na-channels)
- Relative Refractory Period: a period which anew AP can be produced but it takes a larger than normal stimulation
Propagation of the Action Potential
- Entry of Na+ produces a local current. spreads laterally to depolarize adjacent areas of membrane
- Entry of Na+ in the ‘new’ region of membrane produces a local current that spreads to adjacent areas
EPSP and IPSP
Post-synaptic electrical events are graded potentials
- Depolarizing (if Na+ enters): Excitatory Post-Synaptic Potential EPSP
- Hyperpolarizing (if K+ leaves, or Cl- enters): Inhibitory Post-Synaptic Potential: IPSP
General Senses
receptors distributed throughout body 1. Pain (nociceptors) 2. Temperature (thermoreceptors) 3. Touch, pressure, and body position (mechanoreceptors) 4. Chemical stimuli (chemoreceptors) Visceral- internal organs
Special Senses
Receptors congregated in specialized sense organs
- smell (olfaction)
- Taste (gustation)
- sight
- balance/equilibrium
- Sound
Receptive Field and Potential
-Discrimination bewteen two similar stimuli is dependent on the number of receptors within an area of sensory surface
Sensory Transduction
- stimulus arrives at receptor and alters membrane potential of receptor
- receptor potential influences rate of AP production in a sensory neuron
- APs travel CNS along afferent pathway
- CNS interprets/processes these incoming signals
