The Nervous System Psychology Midterm

Dendrites are specialized extensions of a neuron that play a crucial role in receiving signals from other neurons. They contain numerous receptors that bind to neurotransmitters released from the axon terminals of adjacent neurons, allowing for the transmission of information. This input is then integrated and processed by the neuron, influencing its activity and the generation of an action potential if the signals are strong enough. Thus, dendrites serve as the primary site for communication and information gathering in the nervous system.

The typical resting membrane potential of a neuron is around -70 mV, which reflects the difference in ion concentrations across the neuronal membrane. This negative value is primarily due to the uneven distribution of potassium (K+) ions inside the cell and sodium (Na+) ions outside. The neuron's membrane is more permeable to K+, allowing more K+ to flow out, which contributes to the negativity. This resting potential is crucial for the generation of action potentials, enabling neurons to transmit signals effectively.

Sensory neurons operate under the all-or-none principle, meaning that once a threshold is reached, an action potential is generated at full strength. To encode a stronger stimulus, these neurons increase the frequency of action potentials rather than their height. This frequency modulation allows the nervous system to interpret varying intensities of stimuli, with more frequent impulses indicating a stronger stimulus, while the amplitude of each action potential remains constant. Thus, the information about stimulus strength is conveyed through the rate of firing.

Blocking the reuptake of a neurotransmitter at the synapse prevents the neurotransmitter from being reabsorbed by the presynaptic neuron. This leads to an increased concentration of the neurotransmitter in the synaptic cleft, allowing it to remain available for a longer duration. Consequently, the prolonged presence of the neurotransmitter enhances its interaction with postsynaptic receptors, potentially leading to more significant signaling effects in the receiving neuron.

Caffeine functions as an adenosine antagonist because it binds to adenosine receptors but does not activate them. By occupying these receptors, caffeine blocks the effects of adenosine, a neurotransmitter that promotes sleep and relaxation. This antagonistic action leads to increased alertness and wakefulness, as the normal calming effects of adenosine are inhibited. Thus, caffeine's ability to prevent adenosine from exerting its effects classifies it as an antagonist at these receptors.

Myelin is a protective sheath created by glial cells, specifically oligodendrocytes in the central nervous system and Schwann cells in the peripheral nervous system. It facilitates faster signal transmission along axons by insulating them, not slowing it down. However, damage to myelin can disrupt neural communication, leading to various neurological issues. Multiple sclerosis is a condition characterized by the immune system attacking myelin in the CNS, resulting in impaired signal transmission and various symptoms. Thus, the selected statements accurately reflect the role and importance of myelin in neural function.

The 'fight or flight' response is primarily governed by the sympathetic nervous system, not the parasympathetic. The sympathetic system prepares the body for stressful situations by increasing heart rate, dilating airways, and redirecting blood flow to muscles. In contrast, the parasympathetic nervous system is responsible for the 'rest and digest' functions, promoting relaxation, reducing heart rate, and facilitating digestion. Thus, the statement attributing the 'fight or flight' response to the parasympathetic nervous system is incorrect.