Nervous system overview 48 1 Sensory Input Transmit

Nervous system overview (48. 1) • Sensory Input – Transmit information • Light, sound, touch, heat smell, taste, etc • Integration – CNS (central nervous system) • Brain and nerve cord analyzes and interprets • Motor Output – PNS (peripheral nervous system) • carries information into and out of CNS • Transmission triggers an activity or causes an effect such as muscle contraction Fig 48. 3

• Neural cell/Neuron – Branched dendrites • Receive signals from other neurons • Shorter, highly branched – Single axon • Transmits signals to other neurons • Longer – Synaptic terminals (fig 48. 4) • Axons / dendrite junctions • Pass information through chemical neurotransmitters – Glia • Supporting cells to nourish, insulate, and regulate fluids

After gastrulation… • Neural plate forms Brain and embryonic development – Dorsal orientation – “cephal to caudal” direction • Neural tube forms – Infolding of plate, forming groove and crest – Fuses to form tube – Cephal end enlarges = brain – Rest is spinal cord • Mesoderm – Coelom formation – Somites give rise to segmented structures • Endoderm – Gastrovascular development Fig 47. 13

Continued brain development into multiple lobes, enlargements, and extensions Fig 49. 9

• Forebrain Cerebrum – Two hemispheres • • Left: logical, temporal, language Right: Spatial, abstract, artistic, gestalt (perceiving “whole” rather than parts) – Cerebral Cortex • Outer gray matter – Highly infolded (high surface area) • • Sulcus (folds) between gyrus (tissue) Increased s/a = more gray matter and generally more intelligence – Lobes are connected by underlying white matter • Corpus callosum is the main L/R connection – Frontal lobes • Primary motor cortex (motor skills), muscle control, speech, smell, memory, and integration from other areas – Parietal lobes • Somatosensory, touch, pressure stimuli – Temporal lobes • Hearing, balance – Occipital lobes • Visual centers (visualizing an event or how to spell something)

• Thalamus – Two egg-shaped masses – Cerebral sensory impulses and emotional center (limbic system) • Along with Amygdala (fight or flight) – Plays role in process: • Sensation, Motor activities, waking up, learning, memory • Hypothalamus – Connects to pituitary • Stores hormones for regulation in endocrine system – Homeostatic control functions • Autonomic controls, physiological emotions, body temp. , thirst and satiety, circadian rhythms • Hindbrain Brain stem and cerebellum – Pons connects upper and lower center • • – White matter masses connects to cerebrum and cerebellum – Visual and auditory reflex centers Cerebellum • • Midbrain • • Respiratory center with hypothalumus Athletic brain: refining and directing motor activities “athletic memory” Medulla oblongata • Autonomic reflexes: cardio regulatory, blood pressure, respiratory, vomiting, couching

Brain ventricles and CSF • Ventricles are remnants of early hollow tube • Filled with Cerebral Spinal Fluid – Derived from blood plasma; with lots of ions – Liquid cushion – “fatty” brain mass “floats”, protected, supported, w/o rigid or sharp edged structures

Meninges

Meninges 2

Reflex arc

Peripheral Nervous System – radiates to and from CNS & includes Somatic (SNS) and autonomic (ANS) Somatic: mechanoreceptors, pain, chemo-, photo-, thermoreceptors Autonomic: unconscious visceral reception; antagonistic (opp. Effects) ANS Sympathetic ANS Parasympathetic

Taste/smell

Eye

Eye from text

Ear

• Malleus (hammer) • Incus (anvil) • Stapes (stirrup)

Cochlea

Cochlea 2

Basilar/Tectorial Membrane

Saccule/Utricle

Vestibular apparatus

Macula with Otoliths

Cupula of semicircular canal