Nervous & Sensory systems Ch 38

2 parts of Nervous System  CNS = Brain and main nerve cords  PNS = paired cranial and spinal nerves

Peripheral Nervous System  Somatic nerves Motor functions Motor functions Skeletal muscle Skeletal muscle voluntary voluntary (Shown in green) (Shown in green)  Autonomic nerves Visceral functions Visceral functions smooth & cardiac muscle smooth & cardiac muscle involuntary involuntary (Shown in red) (Shown in red)

Fig. 34-4, p.575

Two Types of Autonomic Nerves  Sympathetic  Parasympathetic  Most organs receive input from both  Usually have opposite effects on organ

Sympathetic Nerves  Promote responses that prepare the body for stress or physical activity (fight-or-flight response)  Adrenaline secretion = increase heart rate, glucose released into blood, slow down of housekeeping activities

Parasympathetic Nerves  Promote housekeeping responses such as digestion  Lower heart rate  Glucose uptake

Communication Lines Stimulus (input) Receptors (sensory neurons) Integrators (interneurons) motor neurons Effectors (muscles, glands) Response (output) Figure 34.5 Page 575

Brains…..  A. Most simple = cerebral ganglia  collection of nerves near head  B. Vertebrate brains  1. gray matter: neuron cell bodies, non myelinated axons & glia  2. white matter: axons covered in myelin  3. cerebrospinal fluid fills ventricles in brain  a. filtered from arteries returned to veins  b. supplies nutrients/ carries hormones, removes waste

4. Neuroglia cells  astrocytes – provide support, direct formation of blood-brain barrier (tight junctions)  Oligodendrocytes – make myelin

5. Regions of the Brain  A. Brain Stem: conducts signals from spinal cord to brain, controls homeostasis  (breathing, heart rate, sleep)  1. Hind Brain  a. medulla oblongata  b. Pons  2. Mid Brain (hearing)

 B. Cerebellum – part of hind brain  1. balance  2. motor skills  3. hand-eye coordination

 C. Thalamus – sensory info  D. Hypothalamus – homeostasis  heat  hunger/thirst  hormones  E. Cerebrum –  information processing

Function of the Spinal Cord  Expressway for signals btwn brain & peripheral nerves  Sensory & motor neurons make direct reflex connections in the spinal cord  Spinal reflexes do not involve the brain

Reflexes  Automatic movements in response to stimuli  Reflex arcs: sensory neurons synapse directly on motor neurons  (skip integrators)

Stretch Reflex STIMULUS Biceps stretches. Response Biceps contracts. Figure Page 585 motor neuron sensory neuron

Assessing a Stimulus  Action potentials don’t vary in amplitude  Brain tells nature of stimulus by:  1) Particular pathway that carries the signal  2) Frequency of action potentials (how quickly is signal repeated)  3) Number of receptors signalling

Taste Taste  Chemoreceptors  Five primary sensations: sweet, sour, salty, bitter, and umami sweet, sour, salty, bitter, and umami Figure 35.8 Page 604

Smell  Olfactory receptors  Receptor axons lead to olfactory lobe  Binding molecules triggers action potential olfactory bulb receptor cell Figure 35.7 Page 604

Anatomy of Human Ear cochlea auditory nerve eardrum auditory canal hammer anvil stirrup Fig a Page 614

Sound Reception  Sound waves make the eardrum vibrate  Vibrations are transmitted to the bones of the middle ear  The stirrup transmits force to the oval window of the fluid-filled cochlea

Sound Reception  Movement of oval window causes waves in the fluid inside cochlear ducts Figure 35.11c Page 606 eardrumround window oval window (behind stirrup) scala vestibuli scala tympani

scala vestibuli cochlear duct organ of Corti scala tympani sensory neurons (to the auditory nerve) Fig d, p.607

Sound Reception hair cells in organ of Corti tectorial membrane lumen of cochlear duct basilar membrane lumen of scala tympani to auditory nerve Figure 35.11e Page 607

Fig a, p.607

Vision Vision  Sensitivity to light does not equal vision  Vision requires two components Eyes Eyes Capacity for image formation in the brain Capacity for image formation in the brain

Invertebrate Eyes Limpet ocellus sensory neuron epidermis cuticle lens Land snail eye Compound eye of a deerfly ommatidium Figures & Pages 608 & 609

Fig , p.609 vitreous body cornearetinaoptic tract lens

Human Eye sclera choroid iris lens pupil cornea aqueous humor ciliary muscle vitreous body retina fovea optic disk part of optic nerve Figure Page 610

Organization of Retina  Photoreceptors lie at the back of the retina, in front of a pigmented epithelium  For light to reach the photoreceptors, it must pass layers of neurons involved in visual processing

Organization of Retina  Signals from photoreceptors are passed to bipolar sensory neurons, then to ganglion cells Figure Page 612

 Reference: Reference:  cas/animalphysiology/websites/2003/Mulle r/development%20of%20the%20cephalop od%20eye.htm cas/animalphysiology/websites/2003/Mulle r/development%20of%20the%20cephalop od%20eye.htm cas/animalphysiology/websites/2003/Mulle r/development%20of%20the%20cephalop od%20eye.htm

a Light rays from an object converge on the retina, form an inverted, reversed image. b When a ciliary muscle contracts, the lens bulges, bending the light rays from a close object so that they become focused on the retina. c When the muscle relaxes, the lens flattens, focusing light rays from a distant object on the retina. muscle contracted slack fibers muscle relaxed close object distant object taut fibers Fig , p.611

stacked, pigmented membrane cone cell rod cell Fig , p.612

The Photoreceptors  Rods Contain the pigment rhodopsin Contain the pigment rhodopsin Detect very dim light, changes in light intensity Detect very dim light, changes in light intensity  Cones Three kinds; detect red, blue, or green Three kinds; detect red, blue, or green Provide color sense and daytime vision Provide color sense and daytime vision

Retina to Brain retina optic nerve lateral geniculate nucleus visual cortex Figure Page 613