PARTS OF THE BRAIN Parts of the Brain
PARTS OF THE BRAIN
Parts of the Brain Cerebrum- higherorder thinkingintelligence, memory, sensory processing ◦ ◦ ◦ 2 halves connected by corpus callosum 4 lobes- frontal, parietal, temporal, occipital Lobes are in the same location as corresponding skull bone
Lobes ◦ Frontal Lobe◦ Consciousness, judgement, language, emotion, concentration, problem-solving ◦ Broca’s Area- coordinates muscle movement for speech ◦ Parietal (Par-eye-it-all) Lobe◦ Integrating sensory information, hand-eye coordination ◦ Temporal (Temp-oral) Lobe◦ Smell and sound, memory of visual and auditory patterns ◦ Occipital (Ox-ip-it-all) Lobe◦ Vision
Hemisphere Dominance ◦ Each hemisphere controls motor function for opposite side of body, dominant hemisphere opposite from dominant hand ◦ Dominant (usually left) controls speech, reading, writing, analytical ◦ Non-dominant- emotions, intuition, creativity
Diencephalon ◦ Located between cerebrum and midbrain ◦ Glands contained in diencephalon: ◦ Thalamus- receives sensory impulses, general awareness of touch sensations ◦ Hypothalamus- homeostasis- controls hunger, heart rate, temperature, sleep, etc ◦ Pituitary gland- endocrine gland, secretes important hormones ◦ Pineal gland- endocrine gland, produces melatonin (related to sleep)
Parts of the Brain, cont’d Cerebellum- Balance, posture, coordinates muscle movement Brainstem. Midbrain- visual and auditory reflex centers Pons- regulates breathing, relays nerve impulses from peripheral nerves to brain Medulla Oblongata- regulates heart rate, breathing, blood pressure (sends signals to these functions, while hypothalamus has more of a control function)
Brain Check-up. . . 1. What part of your brain contains your higher-order thinking skills? 2. If you are trying to recognize someone’s face, what area of your brain is going to be active? 3. If you are hungry, what part of your brain is signaling that?
THE SPINAL CORD AND NERVES
Meninges-membranes that surround and protect brain and spinal cord, 3 layers: ◦ Dura mater- outermost, tough connective tissue, blood vessels and nerves ◦ Arachnoid mater- thin, in middle ◦ Pia mater- very thin, innermost, many nerves and blood vessels serve brain and spinal cord
Spinal Cord ◦ Thick bundle of nerves passing through opening at base of skull down through vertebral column ◦ 31 pairs of spinal nerves branch off, control limbs and trunk ◦ Two-way communication system: ◦ Ascending tracts: carry sensory info to brain ◦ Descending tracts: carry nerve impulses from brain to muscles
Peripheral Nervous System Nerves that branch out from CNS and connect it to body parts Two parts: Somatic Nervous System - connects to skin and skeletal muscle, conscious activities Autonomic Nervous System- connects to organs such as heart, stomach, intestines; unconscious activities Central Nervous System Brain and Spinal Cord
Cranial Nerves - originate from brainstem, 12 pairs, control face and neck
Nerve Plexus ◦ Spinal nerves organized into plexuses- complex network of nerves, sort and recombine nerve fibers to correspond to each body part
Autonomic Nervous System Controls heart rate, blood pressure, all unconscious activities 2 Parts. Sympathetic- response to stress, “fight or flight”speeds up heart, breathing, more blood to skeletal muscle Parasympathetic- relaxation, slows down heart, breathing, more blood to digestive organs
◦ Central nervous system ◦ Peripheral nervous system ◦ Parasympathetic nervous system ◦ Sympathetic nervous system Organize these ◦ Autonomic nervous system terms into a concept◦ Brain ◦ Spinal cord map in your ◦ Nerve Plexuses notes. . . think about ◦ Meninges ◦ Cerebellum how they are related ◦ Cerebrum hierarchically ◦ Frontal Lobe ◦ Occipital Lobe ◦ Parietal Lobe ◦ Temporal Lobe ◦ Brain Stem
ANATOMY OF A NEURON
Neuron (Nerve Cell)
Parts of the Neuron ◦ Dendrites- receive nerve impulses ◦ Cell Body ◦ Nucleus ◦ Axon- sends nerve impulses, coated in myelin sheath ◦ Axon Terminals- contact receptors of other cells ◦ Myelin- whitish, fatty material that insulates axon and speeds up signal transmission ◦ Schwann cells- cells wrapped around axon like a jelly roll, makes up myelin sheath ◦ Nodes of Ranvier- gaps between Schwann cells If a cell body were the size of a tennis ball, the axon would be a mile long
Types of Neurons 1. Sensory Neurons (afferent neurons)cell bodies found in a ganglion (group of cell bodies) outside CNS ◦ Dendrites are receptors (sense organs, pain receptors, skin receptors, etc) 2. Motor neurons (efferent neurons)- send messages from CNS to muscles and glands ◦ Cell bodies in CNS, long axons 3. Interneurons- connect motor and sensory neurons, cell bodies located in CNS
NEURON ACTION POTENTIALS
Membrane Potential ◦ Charge difference between inside and outside of cell (called potential difference) ◦ Larger concentration of Na+ ions outside cell and K+ ions inside cell causes charge ◦ In a resting nerve cell, potential difference is called resting potential ◦ Normal resting potential is -70 millivolts (m. V)
Action Potential ◦ Change in neuron membrane polarization and return to resting state is called an action potential ◦ Chain of action potentials form nerve impulse
Action Potential ◦ Stimuli (temperature, light, pressure, other neurons) decrease membrane potential ◦ Decrease is called depolarizing ◦ When threshold potential (-55 m. V) is reached, stimulus is big enough to cause neuron to send a signal ◦ Threshold triggers Na+ and K+ channels located in nodes of Ranvier to open and equalize charges ◦ Na+ channels open faster, causing rapid depolarization ◦ As K+ channels open, membrane becomes negatively charged once more (becomes repolarized) ◦ Adjacent portions of axon are triggered and action potentials propagate down length of axon, making a nerve impulse ◦ Signal “jumps” across Schwann cells from one Node of Ranvier to another ◦ For a short time following impulse (1 -2 milliseconds), a refractory period follows, when membrane returns to resting potential and no action potential can be triggered
Action Potential Video ◦ https: //www. youtube. com/watch? v=7 Eyhs. Oewn. H 4
SYNAPSES AND NEUROTRANSMITTER S
What is a synapse? ◦ Synapse: gap between two neurons ◦ Presynaptic neuron: neuron sending impulse ◦ Postsynaptic neuron: neuron receiving impulse
Synaptic Transmission ◦ Neurotransmitter: chemicals that carry out synaptic transmission ◦ When action potentials reach axon terminals, neurons release neurotransmitters from vesicles ◦ Neurotransmitters travel across synapse, attach to receptors on postsynaptic neuron dendrites
Neurotransmitters ◦ 2 types: ◦ Excitatory- raise membrane potential ◦ Inhibitory- lower membrane potential ◦ Each neurotransmitter can be EXITATORY and INHIBITORY depending on what downstream neuron it is impacting. ◦ Examples: ◦ Acetylcholine- excitatory, muscle contraction ◦ Norepinephrine- excitatory, increases sense of well-being, concentration ◦ Serotonin- inhibitory, causes sleepiness ◦ Dopamine- inhibitory, increases sense of well-being, pleasure
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