Nervous System: Part 2 Organization of the Nervous System The Senses

Nervous System Organization Central Nervous System (CNS) Peripheral Nervous System (PNS) spinal cordbrain Sensory nerves carry sensory information into brain and spinal cord Motor nerves carry motor information from CNS to effectors somatic sensory nerves: signals from skin, muscles, joints, special senses visceral sensory nerves: signals from body organs Somatic motor nerves: signals to skeletal muscles, voluntary Autonomic motor nerves: signals to smooth muscle, cardiac muscle, glands, involuntary Sympathetic division “fight or flight” Parasympathetic division “rest and digest”

Parts of the Brain muscle coordination Cortex: thinking, learning, memory, speech movement, senses breathing, heart rate, blood pressure sends sensory input to cerebrum homeostasis

Spinal Cord and Reflex Arcs white matter ventral root axon of motor neuron axon of sensory neuron cell body of sensory neuron pin dorsal root ganglion cell body of interneuron Dorsal gray matter central canal ventral horn sensory receptor (in skin) effector (muscle) cell body of motor neuron Ventral dorsal horn Involve the Somatic Nervous System

Autonomic Nervous System dilates pupils constricts pupils speeds heart slows heart dilates air passages constricts bronchioles decreases stomach and intestinal activity increases stomach and intestinal activity

Nervous System Case Study: Hemimegalenchephaly Dylan Catania was born with an oversized right hemisphere in his brain that was causing constant seizuresDylan Catania was born with an oversized right hemisphere in his brain that was causing constant seizures His only hope of survival and brain development involved early surgery to sever the connections between the right and left hemispheres of the brainHis only hope of survival and brain development involved early surgery to sever the connections between the right and left hemispheres of the brain

Nervous System Case Study: Hemimegalenchephaly

Nervous System Case Study: Surgery for Hemimegalenchephaly

Nervous System Case Study: Hemimegalenchephaly Dylan has been seizure free since his surgery!

Sensation and Perception Sensation: impulses arrive at cerebral cortex Perception: cortex interprets meaning of sensations

Sensory Areas on Cerebral Cortex

Sense of Vision: Structure of the Eye photoreceptors detect light takes nerve impulses to brain focuses light on retina lens photoreceptors Photoreceptors synapse with neurons that take signal to optic nerve

Sense of Vision: Photoreceptors detects color detects light absorbs light, initiates series of steps leading to nerve signal

Sense of Hearing: Structure of the Ear 1. Sound enters auditory canal 3. Ossicles (bones) of middle ear multiply pressure of vibration 4. Membrane-covered opening transfers pressure to inner ear 5. Pressure enters fluid-filled chamber containing mechanoreceptors 2. Eardrum vibrates slightly due to sound waves

Sense of Hearing: Mechanoreceptors Vibrates in response to pressure in inner ear mechanoreceptor Bend when basilar membrane moves takes nerve impulses to brain

Sense of Taste: Chemoreceptors Taste buds occur along the walls of papillae Molecules bind to receptors on microvilli of taste cells Nerve impulses are sent to brain chemoreceptor Signal from receptor is transmitted within the cell

Sense of Taste Signal Transmission for Salty and Sour Tastes Sodium binds and opens a channel for more sodium to enter Protons bind and open a channel for more protons to enter Release of calcium triggers neurotransmitter release and neuron stimulation

Sense of Taste Signal Transmission for Sweet and Bitter Tastes Internal communication leads to neuron stimulation