Fig. 48.1
Fig. 48.2
Axon endings are called synaptic terminals. They contain neurotransmitters which conduct a signal across a synapse. A synapse is the junction between a presynaptic and postsynaptic neuron.
Here s a simple Nerve Circuit the Reflex Arc. A reflex is an autonomic response (no conscious control). Fig. 48.3
Supporting Cells (Glia). There are several types of glia. Schwann cells are glia found within the PNS. They form a myelin sheath by insulating axons. Fig. 48.5
Measuring Membrane Potentials. Fig. 48.6a An unstimulated cell usually has a resting potential of -70mV.
Ungated ion channels allow ions to diffuse across the plasma membrane. These channels are always open. This diffusion does not achieve an equilibrium since the sodium-potassium pump transports these ions against their concentration gradients. Fig. 48.7
Let s watch these before we look at any more words http://highered.mcgrawhill.com/sites/0072437316/student_view0/chapter 45/animations.html# First watch this Action Potential Propagation in an Unmyelinated Axon
3. Nerve impulses propagate themselves along an axon The action potential is repeatedly regenerated along the length of the axon. An action potential achieved at one region of the membrane is sufficient to depolarize a neighboring region above threshold. Thus triggering a new action potential. The refractory period assures that impulse conduction is one-way. Need a review?
Fig. 48.10
Saltatory conduction. In myelinated neurons, only unmyelinated regions of the axon depolarize. Thus, the impulse moves faster than in unmyelinated neurons, and also requires less energy for the Na-K pumps. Fig. 48.11
4. Chemical or electrical communication between cells occurs at synapses Electrical Synapses. Action potentials travel directly from the presynaptic to the postsynaptic cells via gap junctions. These are fairly rare. Here s the more common kind: chemical synapses.
Chemical Synapses. More common than electrical synapses. Neurotransmitter substances act on membrane proteins (gated-channels) in the post-synaptic membrane. Postsynaptic, chemically-gated channels exist for ions such as Na +, K +, and Cl -. Watch the first animation here http://highered.mcgrawhill.com/sites/0072437316/student_view0/chapter45/an imations.html#
Fig. 48.12
6. The same neurotransmitter can produce different effects on different types of cells Acetylcholine. Excitatory to skeletal muscle. Inhibitory to cardiac muscle. Secreted by the CNS, PNS, and at vertebrate neuromuscular junctions.
Biogenic Amines. Neurotransmitters and hormones. Epinephrine and norepinephrine. Can have excitatory or inhibitory effects. Secreted by the CNS and PNS. Secreted by the adrenal glands.
Dopamine Generally excitatory; may be inhibitory at some sites. Widespread in the brain. Affects sleep, mood, attention, and learning. Secreted by the CNS and PNS. A lack of dopamine in the brain is associated with Parkinson s disease. Excessive dopamine is linked to schizophrenia.
Dopamine is the addiction neurotransmitter No matter how they do it, all addictive substances cause a release of dopamine in the brain, thus stimulating the pleasure center. What can do this? Cocaine, THC, alcohol, meth and SUGAR!!! Yes, sugar has been shown to be addictive, stimulating dopamine release and opioid secretion. High carbs and binge eating are the most addictive pattern.
2. Nervous systems have evolved to show diverse patterns of organization Nerve nets. The simplest nervous systems. Fig. 48.15a, b
With cephalization came more complex nervous systems. Fig. 48.15c-h
3. Embryonic development of the vertebrate brain reflects its evolution from three anterior bulges of the neural tube Fig. 48.19
Here s what the EOC wants you to be able to label Cerebrum, cerebellum, pons, medulla oblongata, brain stem, the 4 lobes frontal, parietal, occipital, and temporal.
Fig. 48.20
Here s a link to make your own brain hat http://teachhealthk- 12.uthscsa.edu/curriculum/brain/pa03pdf/0301B- Cap.pdf
The Medulla and Pons. Medulla oblongata. Contains nuclei that control visceral (autonomic homeostatic) functions. Breathing. Heart and blood vessel activity. Swallowing. Vomiting. Digestion. Relays information to and from higher brain centers.
Pons. Contains nuclei involved in the regulation of visceral activities such as breathing. Relays information to and from higher brain centers.
The Cerebellum. Functions to error-check and coordinate motor activities, and perceptual and cognitive factors. Relays sensory information about joints, muscles, sight, and sound to the cerebrum. Coordinates motor commands issued by the cerebrum. Good athletes have good cerebellums.
6. Regions of the cerebrum are specialized for different functions The cerebrum is divided into frontal, temporal, occipital, and parietal lobes. Fig. 48.24b
Fig. 48.25
Lateralization of Brain Function. The left hemisphere. Dominant in right handers. Specializes in language, math, logic operations, and the processing of serial sequences of information, and visual and auditory details. Specializes in detailed activities required for motor control. The right hemisphere. Dominant in lefties. Specializes in pattern recognition, spatial relationships, nonverbal ideation, emotional processing, and the parallel processing of information.
Alzheimer s Update It was discovered in 2008 that the hippocampus is where Alzheimer s begins due to a build-up of a chemical called A-Beta Protein. A drug and a vaccine are in final trials and may be ready just in time for me. Speaking of memory, THC in marijuana is the greatest inhibitor of short term memory, and is also now known to be highly addictive. It is now the #1 cause of addictions in children.